Improvements in the Manufacture of Scale Beams and the Insertion of Knife Edges therein.
Year: 1895

page_text: Date of Application, 25th Nov., 1895-Accepted, 28th Dec., 1895
Improvements in the Manufacture of Scale Beams and the Insertion
of Knife Edges therein.
I, EDWARD BÖHMER of Schröttersdorf near Bromberg, Germany Manufacturer
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 order to bring into one horizontal plane the knife edges or the fulcra of the
upper or the lower beams used until now for lever balances, the formation of a
bend or knee in the beam was required which not only weakens the material at the
respective spot but renders the manufacturing of the beam expensive and lengthy.
The adjustment of the knife edges on such beams has been done until now by
inserting the knife edges or axes into the beams by the use of moulds or forms, the
knife edge being then brought down to the right height by filing and grinding.
It is obvious that this method of adjusting the knife edges to the scale beams is
roundabout and inexact and can only be done by skilled workmen. Scale beams
so adjusted can be altered after having been adjusted with dishonest intentions
without the illegal alteration being easily noticed. Incorrect position of the knife
edge can be caused in such scale beams also without illegal intention by an
unskilled hand in sharpening or in changing the knife edges. Moreover the knife
edges in the scale beams of the construction used until now cannot be much
broader than double the thickness of the beams since otherwise the support of the
knife edges is too small.
This breadth of the knife edges is however especially in large balances not
properly proportioned to the strain put upon them and rapid wear of the knife
edges and incorrect working of the balance are the result. These inconveniences
are removed in the scale beam constructed according to the present invention.
This beam is distinguished from those above described in being quite straight
and not having its knife edges adjusted by hand work; but being provided with
exact bearing cuts for the knife edges. In the accompanying drawings various
forms of such balance beams are shown in juxtaposition with equivalent beams of
the old construction.
Figs. 1-3 show the balance beamt of a table balance which may be made of
drawn steel. In this entirely straight beam t wedge shaped cuts are made by
means of a milling machine in which cuts the exchangable knife edges s are
inserted and fastened by means of strap plates secured by screws. By forming
them in this way the depth of the bearing cuts for the knife edges and in conse-
quence the required position in height of the edge of the knife edges can be
rendered exact. It will be suitable to have also the knife edges made of drawn
steel having a form of section corresponding with the recesses into which they are
to fit of course they need not be triangular as in Fig. 1, but may have for instance
forms as shown in Figs. 4 and 5. In Fig. 6A is shown an upper beam of former
construction in Fig. 6 one of the new construction as employed in decimal balances.
The beam o in Fig. 64 has the bent form of a knee as above mentioned, while the
beam constructed in accordance with the present invention (Fig. 6) is entirely
straight and provided as above described with wedge shaped recesses for receiving
the exchangable knife edges s. The tare weight hitherto arranged on a separate
guide (Fig. 6A) can with this invention be put directly on the beam (Fig. 6).

page_text: Fig. 7 shows a lever beam of the old construction. Fig. 7 shows one of the
new construction, also intended for decimal balances. The straight lower beam u
shown in Fig. 7 has in comparison with the lower beam in the shape of a knee, as
represented in Fig. 7 another important advantage in permitting a much lower
position of the platform which is of importance especially for putting heavy loads
upon it.
In Fig. 8 a balance beam of the old construction for sliding weight balances is
represented while Fig. 8 shows the construction of such a beam in accordance with
the present invention.
The balance beam shown in Fig. 8 is also made of drawn steel on which in a
known way the sliding weight p is arranged. As in the old construction also here
an especial (separate) bar c for the tare weight is provided.
From the above description it is obvious that in the balance beams of the new
construction alteration of the knife edges by means of filing or grinding cannot
be done without detection. Moreover the knife edges can be exchanged and
replaced by others at any time and by inexperienced hands without affecting in
any way the accuracy of the balance as the knife edge recesses remain always the
same. The knife edges receiving moreover by the shape of the bearing recess a
much better support than in the method of fixing them used until now; the breadth
of the knife edges may be increased in a corresponding measure and brought into
suitable proportion to the strain they have to bear.
Having now particularly described and ascertained the nature of this said inven-
tion and in what manner the same is to be performed I declare that what I
claim is: --
1. A balance beam for lever balances distinguished by its upper and lower edges
being provided with wedge shaped recesses into which exchangable knife edges or
fulcra are put with their edges in such a way that the normal position of the knife
edges is fixed and defined by the depth of the wedge shaped bearing recess in the
balance beam for the purposes described.
2. The combination with balance beams having recesses as described of
exchangable knife edges or fulcra having a section in correspondence with the
adjusted bearing recesses of the beam and adapted to be put into the balance
beam without further adjustment of the edge.
Dated this 25th day of November 1895.
HERBERT HADDAN & Co.,
18 Buckingham Street, Strand, London, W.C., Agents to the Applicant.