Apparatus for mechanically breaking up stone or reinforced concrete

An apparatus designed especially for mechanically breaking up reinforced concrete and comprising a cylinder containing a hydraulically-operated piston connected to a thrust wedge and acting upon two insertion pieces to be inserted in a borehole in the reinforced concrete or in stone. In order to avoid excessive wear and tear on the components by reducing the stresses to which they are subjected, the apparatus comprises a bracing part rigidly joined to the cylinder by tie plates, and the two end faces of the insertion pieces remote from the cylinder are braced against this bracing part, through which the thrust wedge passes when the apparatus is in operation. Thus the end faces of the insertion pieces can slide on the surface of the bracing part when they are driven apart by the advancing wedge.

This invention relates to an apparatus for mechanically breaking up stone 
or reinforced concrete, the apparatus comprising a cylinder, a 
hydraulically-operated piston disposed for longitudinal movement within 
the cylinder, a piston rod, a thrust wedge connected to the piston by the 
piston rod, and two symmetrically-disposed insertion pieces adapted for 
insertion into holes bored in the stone or concrete and each comprising an 
inclined portion having the same angle of inclination as the wedge, the 
insertion pieces being movable away from one another laterally and being 
secured against longitudinal displacement, and the piston being adapted to 
act upon the insertion pieces via the wedge. By means of bearing parts 
fixed to the inner ends of the insertion pieces, the latter are hung 
within a casing which is integral with the cylinder and which also serves 
to guide the piston rod. 
Apparatus of this kind meet various requirements. Among other things, they 
should be portable and capable of producing very great bursting forces, on 
the order of some hundreds of megapoundals, by means of the insertion 
pieces; moreover, even those components which are subjected to the 
greatest stresses, especially the insertion pieces, should be resistant to 
breakage. 
In an apparatus taught by Swiss Pat. No. 454,003, the insertion pieces are 
suspended at their rearward ends, so as to be laterally displaceable, on a 
crossbolt inserted in a casing which is integral with the cylinder and 
also serves to guide the piston rod. Such crossbolts are subjected to 
great beding stresses when the apparatus is in operation. 
In an apparatus of the kind initially mentioned which is described in the 
same Swiss patent as well as in German Pat. No. 1,249,194 (in which 
reference is also made to a great deal of other prior art), the insertion 
pieces are provided at their inner ends with substantially half-round, 
reinforced head portions slidingly seated on a collar which is reinforced 
with a hardened ring in the area of the contact surface and disposed at 
the lower end of the casing. 
In this design, the bearing pressure on the contact surfaces is extremely 
high because these surfaces are so small, one reason for this being that 
in this apparatus, intended for breaking up stone or rock, the aim was to 
be able to insert the insertion pieces in boreholes having as small a 
diameter as possible, which in turn led to correspondingly small 
dimensions of the apparatus. 
In this known design, in order to prevent the head portions from canting in 
the bearing ring, the head portions must slide transversely. However, such 
transverse sliding takes place only if the slide supports between the 
thrust wedge and the insertion pieces reach back over the entire stroke of 
the thrust wedge to the transverse plane containing the contact surfaces 
between the head portions and the bearing ring. Yet even if this 
prerequisite is met, it may happen that the transverse sliding of the head 
portions toward each other does not take place when the thrust head is 
retracted, even though the stone or rock acts upon the insertion pieces at 
a certain distance from the bearing ring, e.g., under the effect of weight 
or--when reinforced concrete is being broken up--through the resilient 
reaction of non-ripped reinforcing bars. Whenever the transverse sliding 
does not take place in one or the other direction, canting occurs at the 
contact surfaces. Canting also takes place when the insertion pieces slip 
out of line under the influence of shearing stresses acting in the 
reinforced concrete. Whenever canting occurs, bending may easily lead to 
damage which can put the apparatus out of order. 
It is an object of this invention to provide an apparatus of the kind 
initially described, especially for breaking up reinforced concrete, which 
is designed in such a way that it not only meets the above-stated 
requirements but also obviates the shortcomings of the known apparatus 
just mentioned. 
To this end, the apparatus according to the present invention further 
comprises a bracing part, a passage in the bracing part for the wedge, and 
two tie plates respectively extending on each side of the wedge, the 
bracing part being rigidly joined to the cylinder by the tie plates, and 
the insertion pieces each having a flat end face at the end thereof remote 
from the cylinder, these end faces being braced against the bracing part. 
In a design such as this, the specific compression between the flat bracing 
faces of the insertion pieces and the associated surfaces of the bracing 
part is reduced to such an extent that there need be no fear of premature 
wear and tear, much less of erosion. What is more, no harmful canting can 
occur since the insertion pieces are freely movable in the transverse 
direction. 
Preferably, the insertion pieces will have a T-shaped cross-section, the 
upright of the T comprising the inclined portion and a slide plate being 
secured to one side of each such upright and displaceably guided along the 
inside of an adjacent tie plate. 
Furthermore, it may be provided that on each insertion piece, the slide 
plate extends up to the front end thereof and back to a stop ledge secured 
to the inside of the adjacent tie plate.

Reference numeral 1 designates a cylinder, shown only in part, in which a 
hydraulically-operated piston 2a is disposed for longitudinal movement. 
The piston is connected via its piston rod 2b to a thrust wedge 2 which 
acts upon two symmmetrically-disposed insertion pieces 3, 4 to be inserted 
in a borehole in the stone or concrete to be broken up. Insertion pieces 
3, 4 can be driven apart laterally and each comprise an inclined portion 
having the same angle of inclination as wedge 2, each such portion being 
provided with a slide surfacing 3a and 4a, respectively, made of bronze or 
the like; the flat, transversely-lying end faces 3b and 4b of insertion 
pieces 3, 4 each form a sliding surface which is braced against a 
corresponding surface of a bracing part 5. The latter has a passage 6 for 
wedge 2 and is rigidly connected to cylinder 1 by two tie plates 7, 8 
extending parallel to the longitudinal axis of wedge 2 on each side 
thereof. 
As may best be seen from FIGS. 3 and 4, insertion pieces 3, 4 are T-shaped 
in cross-section, the upright of the T comprising the inclined portion 
together with the slide surfacing 3a or 4a. Secured to one side of each 
insertion piece 3, 4, e.g., welded thereto (the welding seams being 
designated as 3c, 4c, is a slide plate 9, 10 which is displaceably guided 
along the inside of the adjacent tie plate 7, 8. Welded to the inside of 
each tie plate 7, 8, approximately midway along its length, is a stop 
ledge 11, 12, against which slide plate 9, 10 of the corresponding 
insertion piece 3, 4 comes to rest when wedge 2 is retracted, so as to 
prevent insertion pieces 3, 4 from being pulled back upon retraction of 
wedge 2. 
The mode of operation of the apparatus will be obvious from the foregoing 
description thereof and requires no further explanation. It may be 
worthwhile to mention, however, that before the illustrated operative 
portion is introduced into a borehole in the stone or concrete to be 
broken up, the two insertion pieces may be removed without any difficulty, 
all parts easily cleaned, and the sliding surfaces coated with a 
lubricant. In none of the components do any stresses arise which would be 
difficult to take into account. The transverse path which the insertion 
pieces can travel is very long as compared with the known designs, which 
is an important factor particularly in the mechanical breaking-up of 
rather lean reinforced concrete because there, a long such path is often 
necessary until ripping of the reinforcement takes place.