IMPROVEMENTS IN THE CONSTRUCTION OF WEIGHING MACHINES AND SCALE BEAMS."
Year: 1880

page_text: LETTERS PATENT to William Beilby Avery, of Birmingham, in the County of
Warwick, for an Invention of "IMPROVEMENTS IN THE CONSTRUCTION OF
WEIGHING MACHINES AND SCALE BEAMS."
"
PROVISIONAL SPECIFICATION left by the said William Beilby Avery at
the Office of the Commissioners of Patents on the 20th December 1880.
WILLIAM BEILBY AVERY, of Birmingham, in the County of Warwick.
IMPROVEMENTS IN THE CONSTRUCTION OF WEIGHING MACHINES AND SCALE
BEAMS."
These improvements consist in a novel arrangement of knife edges whereby
great accuracy of register is secured and the uncertain action caused by the lateral
movements of the knife edges on the bearings is prevented. Hitherto the knife
edges used in scale beams and steel yards of ordinary construction have been so
loosely fitted as to expose them to a rubbing and grinding action of the bearing
surfaces, which in a short time has destroyed the sharpness of the knife edges, but
by my improved arrangement of knife edges I entirely prevent all lateral displace-
ment of the parts in contact during the act of loading or unloading the scales,
thereby ensuring the long continued sensitiveness of the knife edge and the
unerring accuracy of the beam or steel yard.
In applying my arrangement of knife edges to an ordinary pair of grocers' scales,
for example, I proceed as follows:-Fitted to each end of the scale beam and
extending at right angles therefrom in a horizontal position is a prism of steel
forming a fixed knife edge for supporting the scale by means of a shackle and chains.
Each of these fixed knife edges has three bearing blocks or stop pieces formed in
one with it, or rigidly secured thereto by set screws or otherwise, two of such
bearing blocks being situate on the outer side of each of the prisms or knife edges,
and the third being attached to or formed on the inner side of each of the knife
edges and intermediate of the other two.
The shackle which rests upon each fixed knife edge is also of peculiar construction;
it consists of a hook of metal, the upper part of which is flat and of such a breadth

page_text: as to pass between the two stop pieces on the outer face of the fixed knife edge,
and it is spread out at the end so as to form a head furnished with two knife edges
at its rear, which knife edges bear against the two stop pieces on the outer face of
the fixed knife edge.
The flat end of the shackle is also slotted to allow of its passing over the stop
piece on the inner face of the fixed knife edge, and this slot is furnished with a
knife edge which bears against the said inner stop. When this shackle is in its
normal position, that is to say, resting upon the fixed knife edge, its flattened upper
part will assume a horizontal position, and each of the knife edges formed in the
shackle will lie in the same horizontal plane which passes through the fixed knife
edge, and all these knife edges will touch and coincide with an imaginary line
drawn horizontally along the edge of any one of them. Thus a vertical section of
the knife edges would show them as all meeting in one point, and however great
may be the dip of the scale beam, the knife edges will experience little or no
lateral rubbing or grinding action, but will continue to rotate round an imaginary
axis.
By this arrangement all lateral movement of the shackle on the fixed knife edge
is prevented by reason of the knife edges with which such shackle is furnished,
and which bear against the blocks or stop pieces screwed on or otherwise attached
to the fixed knife edge.
The above principle of construction may be applied to steel yards with great
advantage over the arrangement of knife edges at present in use; for by reason of
the total absence of all lateral movement or rubbing action of the bearing surfaces
upon the knife edges I am enabled to place the knife edges in such close proximity
to each other that a greatly increased leverage is obtained.
When applying my improved arrangement of knife edges to a steel yard I form
the fixed knife edge with a central block which will divide this knife edge into two
equal parts, and will project slightly on each side of the steel yard through which it
is passed, the projecting portions of the central block serving as bearing surfaces for
knife edges on the inner sides of the shackle to work against. Stop pieces or
bearing blocks are also screwed or otherwise firmly secured to the extremities of
the fixed knife edge for knife edges on the outer side of the shackle to work
against. The shackle is made of U shape, the end of each vertical portion being
bent over and flattened out to form bearing surfaces for the two parts of the fixed
knife edge to work against. Each of the flattened ends of the shackle has an inner
and an outer knife edge which work against the stop pieces or bearing blocks on
the fixed knife edge, as already described, and prevent all lateral movement or
rubbing action of the shackle upon the fixed knife edges.
The sharp portions of all the knife edges when the shackle is in position will, as
before, touch and coincide with an imaginary line drawn along the edge of any one
of them.
The above arrangements may be used in an inverted position with slight
modifications if necessary to suit any peculiarities in the construction of the steel
yards and scale beams to which they are to be applied, but the principle of con-
struction to be observed throughout will be the same as is above indicated.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said William Beilby Avery in the Great Seal Patent Office on the
18th June 1881.
WILLIAM BEILBY AVERY, of Birmingham, in the County of Warwick.
"IMPROVEMENTS IN THE CONSTRUCTION OF WEIGHING MACHINES AND SCALE
BEAMS.'
"
These improvements consist in a novel arrangement of knife edges for the beam
and shackles of weighing machines and steelyards whereby great accuracy of
register is secured and the uncertain action caused by the lateral movements of the
knife edges on their bearings is prevented.
Hitherto the knife edges used in scale beams and steel yards of ordinary con-
struction have been so loosely fitted as to expose them to a rubbing and grinding
action with or against the bearing surfaces, which in a short time has destroyed the
sharpness of the knife edges, but by my improvements I entirely prevent all lateral
displacement of the parts in contact during the act of loading or unloading the
scales, thereby ensuring the long continued sensitiveness of the knife edges and the
unerring accuracy of the beam or steelyard.
In Sheet I. of the accompanying Drawings I have shewn the Invention as applied
to a steel yard, Fig. 1 being a side elevation of the steel yard complete, with the
exception of the shackle, which is to carry the weight; Fig. 2 is a plan or edge
view of the steelyard beam with the shackles removed to shew the horizontal and
vertical bearings of the beam; Figures 3 to 7 shew in several views one of the
knife-edged pieces which is intended to rest upon or to carry a shackle or bearing
of peculiar construction. This shackle or bearing is shewn detached in several
views at Figures 8 to 11, and it may be used in either of two positions, both of
which are illustrated in Fig. 1. A is the graduated beam provided with knife-
edged bearing pieces at B, C; the knife-edged piece at B rests upon a suspended
shackle E, which supports the whole weight of the steelyard and its load. From
the knife-edged piece at C hangs a shackle F, from which the load to be weighed
depends. G is an ordinary balance weight for adjusting the balance of the steel-
yard. The knife-edged bearing pieces at B and C are of precisely the same
construction, but the position of the two in the beam is reversed to allow of the one
resting upon a supporting shackle and the other receiving a shackle to be supported.
The bearing piece shewn in plan view at Fig. 3 is formed with a vertically set
knife edge a (see the cross section, Fig. 6), which is virtually divided into two by a
central block b intended to fit a slot formed for it in the beam A.
The face of this central piece, which coincides with the vertical face of the knife
edge, and is shewn in face view at Fig. 4, forms a bearing surface for a divided
horizontal knife edge of the shackle, as will be presently explained. Fitted to the
vertical face of the bearing piece and at the extremities of the knife edges a (see
Fig. 7) are the pieces c, c, which project beyond the knife edges, and near their
extremities form bearing surfaces (shewn in front view at Fig. 5) for a second pair
of horizontal knife edges of the shackle.
This shackle is shewn in plan view at Fig. 8, in end view at Fig. 9, in cross
section at Fig. 10, and in side view at Fig. 11. It consists of a loop of iron
with its extremities bent over at right angles and flattened. The opposite sides of
the flattened and turned over ends of the shackle are rebated, as shewn in the
plan view, Fig. 8, in order to form two pairs of horizontal knife edges h, h, and i, i,
which edges are all in line, and are intended when in place on the bearing piece to
range with the knife edges a. The underside of the turned over ends of the shackle

page_text: are made smooth, and form bearing surfaces k, k, for the knife edges a, upon which
the shackle will be free to rock, as heretofore, to allow it to regain its normal
position, as the position of the steelyard bar may vary. It is to limit the shackle
to this rocking motion that the present improvements are designed; thus the knife
edges h will find a bearing on the vertical bearing surface b, and the knife edges i
on the vertical bearing surfaces c.
It will now be understood that when the shackle is in place on the beam all the
knife edges will touch and coincide with an imaginary line drawn horizontally
along the edge of any one of the knife edges a, h, or i; thus a transparent vertical
section of the knife edges would shew them as all meeting in one point.
It will now be understood that however great may be the dip of the beam the
knife edges will experience no rubbing or grinding action, but will continue to rock
on an imaginary axis.
Sheet II. shews the Invention as applied to an ordinary scale beam, and also to
a counter weighing machine. Fig. 12 is a side view of a scale beam with its
central support and the shackles at its opposite ends for carrying, the one the
weighing scale and the other the weight scale; Fig. 13 is a plan view of the same;
Fig. 14 is a cross section on the line 1, 2, of Fig. 12; and Fig. 15 is an end view of
the beam with a shackle appended thereto. In these Figures a are the vertically
set knife edges made fast to the centre and the opposite ends of the beam A,
and formed in one piece with them, as before explained, are the bearing surfaces b.
The ends also of the knife edges are fitted, as before, with end bearing pieces c.
The balance beam is supported at its centre on two blocks H, H, which are con-
structed in principle like the shackles before mentioned, that is to say, they are
each provided with horizontal knife edges h, i, for bearing respectively against the
surfaces b, c, for the purpose of steadying the beam, and preventing its moving
endwise when a load or a weight is placed in or removed from one of the pendent
scales. These blocks H, in order to insure a level bearing for the central knife
edges a of the beam, are attached to their support by means of horizontal pins
running transversely of the knife edges a, which mode of attachment enables them
to adjust themselves to the desired level. The shackles F, F, somewhat differ in
construction from the shackle E of the steel yard, inasmuch as in this case they do
not require that their bearing surface shall be cut through to permit of their attach-
ment to the beam. The portion of the shackle which constitutes the bearing
surface for the knife edges a, and in which the knife edges h and i are formed,
consists of a slotted plate, to which the loop of the shackle is attached by rivetting.
As regards the principle of construction the shackles in this as in the former
example are identical. Fig. 16 shews in side elevation so much of a counter
weighing machine as will serve to explain the mode of applying my Invention to
that class of machines; Fig. 17 is a plan view, and Fig. 18 is an end view of the
same. In these Figures A is a rocking frame which carries the pans or plates for
receiving respectively the weights and the goods to be weighed. Formed on the
transverse bars of this frame are the knife edges a, upon which rest a pair of
blocks H, H, similar to those in the last described arrangement, and now employed
for carrying the pans or plates which are to receive the weights or goods to be
weighed. The pan or plate is fitted on its underside with two pairs of lugs which
embrace the blocks H, and are intended to receive the pins which connect the
blocks and plate or pan together. The rocking frame A is mounted, as usual, on
central bearing blocks provided with check pieces or stops, which prevent the
endway motion of the frame and the rubbing of the knife edges upon the bearing
blocks.
Having now set forth the nature of my Invention of "Improvements in the
Construction of Weighing Machines and Scale Beams," and explained the manner
of carrying the same into effect, I wish it to be understood that under the above in
part recited Letters Patent I claim,-
The use in connection with the vertically set knife edges of steelyards, scale
beams, and other weighing machines of bearing surfaces, such as b, c, for receiving

page_text: the pressure of horizontal knife edges, such as h, i, carried by pendent or supporting
shackles or bearing blocks, all such knife edges (when they are in place) coinciding
in an imaginary line drawn along any one of such edges, as and for the purpose
above set forth.
In witness whereof, I, the said William Beilby Avery, have hereunto set my
hand and seal, the Seventeenth day of June, in the year of our Lord One
thousand eight hundred and eighty one.
WILLIAM BEILBY AVERY. (L.S.)