Precision tweezers with removable terminals

The invention relates to a pair of precision tweezers (1) with two tines (2, 3), each of which has a terminal (10, 11), each terminal (10, 11) having a pair of calibrated cylindrical projections (10i, 11i) capable of entering a pair of holes (4, 5 and 6, 7) in the respective tine (2, 3), wherein the pair of holes (6, 7) in one (3) of tines (2, 3) is comprised of a hole which is cylindrical (6) and a hole which is oblong (7) in the transverse direction with respect to the longitudinal axis of said tine (3), and the pair of holes (4, 5) in other tine (2) is comprised of two holes which are oblong in the direction of the longitudinal axis of the tine.

This invention relates to the field of precision tweezers with two 
terminals attached reversibly on the free ends of the two tines which form 
the tweezers. 
To obtain an exact alignment between the terminals themselves and between 
the terminals and the respective tines, on each of the latter--according 
to the prior art--there is a pair of calibrated cylindrical holes parallel 
to one another, into which are inserted cylindrical projections, also 
calibrated, which are joined to the terminal to which it will be attached. 
Once the precise alignment of the parts has been determined, the terminals 
are then secured to the tines using a known attachment system, for example 
one comprised of a screw and holes present on the tine and on the 
terminal, the hole on the latter being threaded. 
This attachment system is obtained by leaving predetermined spaces between 
the screw and the hole in the tine in such a way as to allow attachment of 
the parts after having defined the alignment, independently of a possible 
shifting between the axes of the two holes, one of which, as was mentioned 
above, is threaded, and through which the attachment screw passes. 
This system of alignment and attachment yields a sufficient degree of 
precision when the terminals are made of metal, but has some limitations 
when for example these terminals, whether made of metal or ceramic 
materials, are heat-treated to improve physical characteristics, for the 
purpose of obtaining better resistance to wear, better resistance to 
combined compressive and bending stress, and better electrical or thermal 
conductivity, etc. 
In this case, between the two terminals of a pair of tweezers such as this 
one, due to the residual internal (not necessarily isotropic) stresses in 
the material after said heat treatments, dimensional differences may 
appear, manifested either in total length or in alignment with the 
respective tines. 
This in turn leads to imperfect superposition of the points of the 
terminals on the assembled tweezers, with a noticeable adverse effect on 
the precision of the delicate operations the tweezers are designed to 
carry out. 
To avoid the aforementioned disadvantages, the inventor of this invention 
has designed a pair of precision tweezers which always enable perfect 
superposition of the points, whether or not there are dimensional 
differences between the two terminals. 
This is accomplished by making the holes with a particular shape and with 
particular dimensions which allow the terminals to be aligned so as to 
ensure the aforementioned desired result. This will be explained in 
further detail below. 
In particular, the object of this invention is a pair of precision tweezers 
as defined in the preamble of claim 1 appended hereto, characterized by 
the characterizing part of this claim.

It can be observed in FIG. 2 that at the end of tine 2 there are three 
holes aligned with one another: center hole 9 is shaped in such a way as 
to accommodate, with a predetermined amount of play, the head of an 
attachment screw (not shown). 
The two holes 4, 5 arranged laterally on either side of this center hole 9 
have a width extending in a direction transverse to longitudinal axis h--h 
of tine 2 enabling snug accommodation of two cylindrical projections 10i 
present on terminal 10 which are to be attached, but are oblong (therefore 
in an approximately elliptical shape) in the direction of this axis h--h, 
in such a way as to allow a predetermined degree of axial travel of the 
entire projection 10i (see arrows A-E) when they are inserted in these 
holes 4, 5 (an enlarged view of aforementioned holes 4, 5, 9 is given in 
FIG. 4). 
It can be observed in FIG. 3 moreover that at the end of other tine 3 there 
are three holes in alignment: center hole 8 is identical in function and 
shape to hole 9 described above, but of holes 6, 7 arranged laterally on 
either side of the center hole, hole 6 which is farther away from the free 
end of tine 3 is cylindrical, and calibrated in such a way as to snugly 
accommodate one of two cylindrical projections 11i of terminal 11 which 
are to be attached to tine 3, and hole 7 closer to the free end of tine 3 
has a width extending in the direction of longitudinal axis K--K of the 
latter slightly greater than or equal to the diameter of other cylindrical 
projection 11i of the terminal, and has a greater length, therefore being 
oblong in the direction perpendicular to this axis K--K, so as to allow a 
predetermined degree of travel of the projection coupled to it in two 
opposite directions (see arrows C-D) transversely to this longitudinal 
axis K--K of tine 3. 
In other words, when projections 11i are inserted in holes 6, 7, one of 
them, the one inserted in cylindrical hole 6, can rotate around its own 
axis, and the other inserted in oblong hole 7 can travel in one of the 
aforementioned directions C or D. 
Since this travel actually delineates the arc of a circle with very small 
diameter, hole 7 is consequently made like a rest on the circle arc: given 
the extremely small dimensions of the travel it is still possible to 
obtain the desired adjustability with hole 7 of approximately elliptical 
shape as in FIG. 5 and with a width in the direction of this axis K--K 
just slightly greater than the diameter of these cylindrical projections 
11i. 
These projections can also have various diameters with consequently diverse 
sizes of the actual holes, still yielding the same results. 
With pair of precision tweezers 1 as described above, and as shown in FIG. 
1, it is possible to do the following: two terminals 10, 11 are installed 
on respective tines 2, 3; before tightening the aforementioned attachment 
screws (not shown) in the respective pairs of aligned holes 9-12 and 8-13 
(of which 12, 13 of terminals 10, 11 are threaded), the positioning of 
terminal 10 is adjusted in directions A-E along the h--h axis of tine 2 in 
such a way that its point 10p is precisely superimposed lengthwise on lip 
of the other terminal 11, which is engaged as a fixed reference element in 
the longitudinal direction since it cannot travel axially. 
The configuration of holes 4 and 5 on tine 2 allows terminal 10--positioned 
as described above--to be aligned perfectly with this tine 2, and to be 
perfectly superimposed lengthwise on the other terminal 11, since terminal 
10 can be fixed in this position with its above described attachment screw 
which is not shown in the diagrams. 
At this point, if other terminal 11, as the result of small dimensional 
variations, does not have point 11p perfectly aligned and point 10p of 
terminal 10 is already attached, all that is required is to rotate it a 
small amount in the direction of arrows C and D until points 10p and 11p 
are perfectly superimposed, and then effect definitive attachment with the 
aforementioned attachment screw, which is not shown. 
This invention will allow perfect control of the configuration of the point 
of precision tweezers 1, whether or not there are small dimensional 
differences between the two terminals 10, 11, thereby attaining the object 
which the inventor set for himself. 
It is to be understood that although a preferred embodiment of the 
invention has been described, various other embodiments and variations may 
occur to those skilled in the art. Any such other embodiments and 
variations which fall within the scope and spirit of the present invention 
are intended to be covered by the following claims.