IMPROVEMENTS IN WEIGHING APPARATUS OR MACHINERY
Year: 1879

page_text: LETTERS PATENT to John Parnall, of 21 and 22, Narrow Wine Street, Bristol,
in the County of Gloucester, Scale and Weighing Machine Maker, for the
Invention of "IMPROVEMENTS IN WEIGHING APPARATUS OR MACHINERY."
PROVISIONAL SPECIFICATION left by the said John Parnall at the Office of
the Commissioners of Patents on the 20th November 1879.
JOHN PARNALL, of 21 and 22, Narrow Wine Street, Bristol, in the County of
Gloucester, Scale and Weighing Machine Maker. "IMPROVEMENTS IN WEIGHING
APPARATUS OR MACHINERY."
The first part of my present Invention relates to improvements in that class of
compound lever balances described in the Specification of former Letters Patent
granted to me the 24th day of October, A.D. 1876, No. 4124; also in ordinary
compound lever balances in which single compensating levers are used, and in certain
forms of single lever balances usually termed "Robervabl" balances, in all of which
above mentioned balances agate has not hitherto been used as a bearing surface for
the knife-edges of the centres to work upon.
According to this part of my Invention I construct central bearings of metal
which are made open at the ends to receive blocks of agate for the knife-edges of
the centres to work upon. These blocks of agate are protected on their inner and
outer surfaces by hardened metal, forming friction-plates for the shoulder or point
of the knife-edged centre-pin to work against, as may be required. The end bearings
are constructed to receive similar blocks of agate and work in a similar manner.
In cases where it is desirable to reduce the oscillation in ordinary compound lever
balances I increase the length of the compensating levers, by which means I am
enabled to apply larger platforms to these balances than have hitherto been prac-
ticable, and the liability of the platforms to tip up or cant when loaded is materially
lessened; the balances are also rendered more useful, and less liable to derangement
in working, than such balances as ordinarily constructed. In single lever balances
I construct suitable metal frames, in which agate blocks are inserted for the knife-
edges of the centres to work upon.
By the construction of the parts as above described I am enabled to apply agate,
as a bearing for the knife-edged centres to work upon, to compound and single lever
balances, in which steel only has hitherto been used, the advantages derived from

page_text: this application of agate being greater accuracy and sensitiveness in working, and
greatly increased durability.
My Invention relates, secondly, to an improved suspender for scales of that class
usually termed hand scales.
In carrying this part of the said Invention into practice I construct the suspender
in one piece, instead of two pieces, as heretofore. I saw through the lower end of
the suspender in the process of making the same, and insert a small screw to bind
the divided parts together; provision is thus made for springing the beam in or out
of the suspender in the process of manufacture, and also for repairs at any time they
may be necessary.
By means of this construction I obtain a rigid suspender, in which the width
between the friction-shoulders or points will not vary in use, as commonly occurs in
ordinary suspenders made in two parts with a movable pendant, and accuracy in
the working of the scale is secured.
My Invention relates, thirdly, to an improved device or appliance for relieving
the knife edges of scale-beams, and thereby preventing injury to the same during
the process of placing the goods to be weighed upon or removing them from the
platforms of the said scales.
According to this part of my Invention I construct a suitable iron frame or bearing
bar, which is formed with two V-shaped edges facing each other; a rack is also
formed with two inverted V-shaped edges, which work into the V-shaped edges of
the bearing bar. One end of this rack works through a boss formed on the bearing
bar, and is screwed at its extremity to receive a plate which carries the load or
weight, which otherwise would rest on the knife edges of the scale beam; the said
rack gears into a toothed wheel on a bar or shaft connected with a lever for the
purpose of putting the said relieving apparatus in motion.
My Invention relates also to an improvement in beams or indicators to be used
in scales and weighing machines.
According to this improvement I construct beams or index plates with the
divisions and figures cast upon them and raised above the surrounding metal,
instead of forming the divisions and figures by stamping or cutting lines below the
surface, as heretofore; the said beams or index plates are made in various shapes, as
may be best adapted to suit the form of scale to which they are applied.

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 20th May
1880.
JOHN PARNALL, of 21 and 22, Narrow Wine Street, Bristol, in the County of
Gloucester, Scale and Weighing Machine Maker. "IMPROVEMENTS IN WEIGHING
APPARATUS OR MACHINERY."
The first part of my present Invention relates to improvements in that class of
compound lever-balances described in the Specification of former Letters Patent
granted to me the 24th day of October, A.D. 1876, No. 4124; also in ordinary
compound lever-balances in which single compensating levers are used, and in certain
forms of single lever-balances, usually termed "Roberval" balances, in which above
mentioned balances agate has not hitherto been used as a bearing-surface for the
knife-edges of the centres to work upon. Under the terın agate, as herein used, I
include similar hard minerals.
Figure 1 is a perspective view of a central bearing, and
Figure 2 is a similar view of an end bearing constructed according to my
Invention.
Figure 3 is a front elevation.
Figure 4 is a plan or top view, and
Figure 5 an end elevation of my improved compound lever balance, with the box
or frame in section.
Figures 6 and 7 are perspective views of one of the central bearings, and one of
the end bearings of the same.
Figure 8 is a side elevation with the casing in section, and
Figure 9 is a plan or top view, with portions removed, of a single lever balance,
usually termed a "Roberval" balance, with my improvements applied to the same.
Figures 10 and 11 are elevations, with the box in section, of the end and central
bearings of the said balance.
Figure 12 is a perspective view, drawn to an enlarged scale, of one of the end
bearings and adjacent parts, and
Figure 13 is a similar view of one of the central bearings of the same.
Figure 14 is a side elevation.
Figure 15, a plan with the cover removed, and
Figure 16, a central section of a modified form of single lever balance and its box
or frame.
Figure 17 is a front elevation of an ordinary box end beam provided with my
improved suspender, and
Figure 18 is an end elevation of the said suspender.
Figure 19 is a front elevation, and
Figure 20 is a plan of my improved iudex plate provided with divisions or
indexes on both sides, and
Figures 21 and 22 are similar views of one of my improved index plates with
divisions on one side only.
Like letters indicate the same parts throughout the Drawings.
In constructing central bearings according to my Invention, as shewn at A in
Figure 1 of the Drawings, I form the same of iron or other suitable metal, provided

page_text: with openings to receive blocks a of polished agate for the knife-edges of the centres
or centre pins to work upon; these blocks of agate are protected by plates 6 of
hardened metal, such as steel, inserted at the back of the said agate-blocks, and
forming friction-plates for the shoulders, or friction-points of the knife-edged centre-
pins to work against.
B, Figure 2, represents one of my improved end bearings, which are provided
with agate-blocks a and with hardened plates b, in a similar manner to and for the
same purpose as the corresponding parts in the bearings A.
The central bearing, Figure 1, is intended to be employed instead of the steel
bearing b, and the end bearing, Figure 2, instead of the steel bearing c, shewn in and
described with reference to Figure 2 in the Specification of the aforesaid former
Letters Patent.
In Figures 3 to 7 I have shewn the application of my improved agate bearings to
a compound lever balance. A, A, represent the central bearings, and B, B, the end
bearings; C, C, are the compensating levers. The central bearings A, A, are con-
structed of iron or other metal, and provided with polished agate blocks a, as above
described, for the centre pin to work upon. The inner and outer surfaces of the
agate-block is protected by a steel plate inserted into the central bearing, or the
metal of which the said bearing is composed is case-hardened and constitutes a
friction-plate, as shewn at b¹, for the shoulder of the centre pin to work against.
The end-bearings are also provided with agate blocks a for the knife-edge of the
centre pin to work upon, as above described, in this case a thin plate of steel b
is inserted at the back of the agate block to form a friction plate for the point of
the centre pin to work against.
In some cases, where it is desirable to reduce the oscillation, I increase the length
of the compensating levers C, by which means I am enabled to apply larger plat-
forms to these balances than have hitherto been practicable, and the liability of the
platforms to tip up or cant when loaded or when goods are being weighed is
materially lessened. The balances are also rendered more useful, and less liable to
derangement in working, than such balances as ordinarily constructed. In single-
lever-balances I construct suitable metal frames, in which agate blocks are inserted
for the knife-edges of the centres to work upon.
I also apply the above described agate-bearings to ordinary compound lever
balances, in which the end bearings are fixed to the frame or support which carries
the goods to be weighed, that is to say, to balances similar to that shewn in and
described with reference to Figure 4 in the Specification of the said former Letters
Patent. If desired, the central bearing A above described may be modified in shape
and arranged to work in the same manner as the end bearing B. The other parts
of the balance which are not herein described are of the ordinary construction, and
therefore will be readily understood by those familiar with the subject to which this
Invention relates.
By the construction of the parts as above described I am enabled to apply agate,
as a bearing for the knife-edged centres to work upon, to compound and single lever
balances, in which steel only has bitherto been used, the advantages derived from
this application of agate being great accuracy and sensitiveness in working, and
greatly increased durability.
In Figures 8 to 13 I have shewn a single-lever balance of the class known as
"Roberval" balances provided with agate bearings according to my Invention.
A, A, represent the central bearings, which are arranged to receive blocks of polished
agate, as shewn at a, and steel friction plates 6 for the ends of the centre pin to
work against, as hereinbefore described; B, B, are the end frames or bearings, which
are also formed at each end with cavities to receive the blocks of agate a and steel
friction-plates b. If desired, an oscillating or rocking motion may be imparted to
the central bearings A by connecting them together by a bar and mounting them
on two uprights, in the same manner as practised in other forms of scales hitherto

page_text: constructed; this central bearing is fitted with a cap for excluding dirt from the
agate block, and secured to the bearing by a screw.
Figures 14, 15, and 16 shew a box or frame D for enclosing my improved single
lever balance, and which is also applicable for enclosing steel bearing balances, so con-
structed as to protect the centres and bearings from rust or injury, and facilitate the
manufacture of the balances. In these Figures is also shewn an improved index-
needle and index-plate for obtaining greater accuracy and quickness in weighing.
The box or frame D is composed of metal or other material, and provided at its
central part on each side with a slot or recess, into which either an agate or steel
block c is inserted for the centre-pin to work upon; one of these slots also allows
an index-needle d to be connected to the centre-pin. E is an index-plate, which is
either cast on the box or formed separately and affixed thereto, and adjacent to
which the needle d moves; this needle has a hole at one end, and is passed over the
said centre-pin, its other end being formed with a point corresponding when the
scales are equally balanced with a similar point on the centre of the index-plate E.
A friction plate c¹ is affixed to the front of the frame for the point of the centre-
pin to work against, and also to secure the bearing in position. The platform F
is fitted on its underside with an adjusting cup e, whereby any inaccuracy of the
balance can be regulated from time to time by placing shot or lead therein; the
cover or lid D¹ is secured to the frame by a screw at each end. The other parts
of the balance are similar to those shewn in Figures 8 to 11, with the exception
that the fork G is in a reverse position, and is secured to a bar which unites the
two sides of the frame D.
Another part of my Invention relates to an improved suspender for scales of that
class usually termed hand-scales.
In carrying this part of the said Invention, which is illustrated in Figures 17
and 18, into practice I construct the suspender in one piece, instead of in two pieces,
as heretofore, the said suspender and the beam I being preferably formed of gun-
metal. I divide the lower end of the suspender H by sawing in the process of
making the same, and insert a small screw h' to bind the divided parts together;
provision is thus made for springing the beam in or out of the suspender in the
process of manufacture, and also for repairs at any time they may be necessary.
By means of this construction I obtain a rigid suspender, in which the width
between the friction-shoulders or points will not vary in use, as is commonly the
case in ordinary suspenders made in two parts with a movable pendant, and accuracy
in the working of the scale is secured.
Another part of my Invention, which is illustrated in Figures 19 to 22, relates to
an improvement in beams, index plates, or indicators to be used in scales and
weighing machines.
According to this improvement I construct beams or index-plates with the
divisions or indexes and figures formed by pressure or cast upon them, and raised
above the surrounding metal, as shewn, instead of forming the divisions and figures
by stamping or cutting lines below the surface, as heretofore. These divisions may
be formed on both sides of the plate or beam, as shewn in Figures 19 and 20, or on
one side only of a plate, as shewn in Figures 20 and 21, the other side being plain
and adapted to be inserted into a recess planed or cast to receive it. The said
beams or index-plates can be made or formed in various shapes, as may be best
adapted to suit the varied classes of scales to which they are to be applied.
Having thus fully described the said Invention, and the manner of performing the
same, I wish it understood that I claim,-
First. The employment in a compound or single lever balance of central and end
bearings, with agate surfaces, constructed and arranged for the knife-edges to work
upon, substantially as above described with reference to the Drawings and for the
purposes specified.
Second. The novel construction of suspenders for hand-scales or box-end beams,
substantially as above set forth and for the purposes specified.

page_text: Third. An index-plate or beam having the divisions and figures cast or otherwise
formed thereon, and raised or projecting from the surface of the surrounding metal,
as above set forth.
In witness whereof, I, the said John Parnall, have hereunto set my hand and
seal, this Nineteenth day of May, in the year of our Lord One thousand
eight hundred and eighty.
JOHN PARNALL. (L.S.)