APPARATUS TO BE USED IN BLASTING ROCK
Year: 1883

page_text: PROVISIONAL SPECIFICATION left by the said Herbert Newton Penrice at
the Office of the Commissioners of Patents on the 21st May 1883.
HERBERT NEWTON PENRICE of Witton House near Norwich
IN APPARATUS TO BE USED IN BLASTING ROCK
"
"IMPROVEMENTS
This Invention has for its object improvements in apparatus to be used in
blasting rock, and in machinery adapted for its use in driving headings and
shafts.
In blasting rock it is usual after the blast hole has been made and the cartridges
inserted to close the mouth with a tamping of clay, sand, or other material. This
method fails to utilise anything like the full force of the charge and the tamping
is often blown out with no other result than an injurious enlargement of the
blast hole.
Now according to my invention I confine the charge in the blast bole with a
metal holder. The two ends of the holder fit the hole as pistons before and behind
the charge and they are connected by a spindle or by a cylindrical case with one
or more longitudinal apertures according to the work to be done. This holder
serves two purposes it so connects the piston ends that they can only be separated,
to release the charge, by tearing it asunder, the resistance causing a most efficient
tamping, and it also allows of the force of the explosion being directed where it
is required.
The outer end of my charge holder terminates in a cone beyond the piston
round which sand or any other tamping may be rammed very hard as the blow
cannot reach the explosive..
The section of the holder is made rather less at the inner piston end (which
touches the rock and is made as gas tight as possible) than at the outer end so
that it may break there, and be easily repaired.
Intermediate pistons may be placed at intervals to increase the effect to almost
any extent,

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Herbert Newton Penrice in the Great Seal Patent Office on the
21st November 1883.
HERBERT NEWTON PENRICE of Witton House near Norwich
IN APPARATUS TO BE USED IN BLASTING ROCK
"
"IMPROVEMENTS
This Invention has for its object improvements in apparatus to be used in
blasting rock.
In blasting rock, it is usual after the blast hole has been made and the cartridges
inserted to close the mouth with a tamping of clay sand or other material. This
method fails to utilize anything like the full force of the charge and the tamping
is often blown out with no other result than an injurious enlargement of the
blast hole.
Now according to my invention I confine the charge in the blast hole with
metal holders. The two ends of the holder fit the hole as pistons before and
behind the charge and they are connected by a spindle or by a cylindrical case
with one or more longitudinal apertures according to the work to be done. This
holder serves two purposes; it so connects the piston ends that they can only be
separated to release the charge by tearing it asunder, the resistance causing a nost
efficient tamping and it also allows of the force of the explosion being directed
where it is required.
The outer end of my charge holder may terminate in a cone beyond the piston
round which sand or any other tamping may be rammed very hard as the blow
cannot reach the explosive.
Intermediate pistons may be placed at intervals to increase the effect to almost
any extent.
In order that my said invention may be understood and readily carried into
effect I will proceed to describe the Drawings hereunto annexed.
Figure 1 is a side elevation.
Figure 2 an end elevation.
Figures 3 and 4 are transverse sections of a metal charge holder or tamping
trough constructed in accordance with my invention. The drawing shows the
instrument about one half the actual size but the scale may be varied. The holder
shown is suitable for a hole about ten feet long but these dimensions may be
varied to suit the nature of the rock and other circumstances. It is of a cylindrical
form with a cavity in it upon one side. It is closed at the ends and may advan-
tageously also be provided with as the drawing represents intermediate partitions
which are perforated or vented so that one part of the charge may fire another.
It is of such a size as to enter freely into the blasting hole formed in the rock and
to fit it accurately.
In some cases in order to admit of a more accurate fit I make the charge holder
in separate lengths and insert two or three comparatively short charge holders
into the same blast hole. In this case vents are provided to communicate the fire
from one charge to another.
This charge holder when required for use is filled with a powerful explosive,
dynamite or blasting gelatine are the explosives which I prefer to employ.
When so charged it is introduced into the hole of the rock and a suitable fuse is
applied.
The outer end of the hole beyond the charge holder is then tamped or closed in
the usual way. The outer end of the charge holder may be coned to facilitate
this tamping but it is not so shown in the drawing. Care is taken in placing the

page_text: charge holder in the hole that its open side shall be turned in the direction in
which it is desired that the force of the explosion should be expended.
When it is desired that the force of the explosive should be exerted equally all
around the blasting hole-a central spindle connecting two end discs is then used
and in this case also there may be intermediate discs.
The charge is arranged around this spindle and is suitably enveloped to retain
it in position whilst putting the charge holder into the blasting hole.
Or the charge holder may be made as a complete cylinder with closed ends and
either perforated at the sides or otherwise but the arrangements previously
described are preferable. In any case the tensile strength of the charge holder
should be very.considerable and comparable with the pressure generated by the
explosion of the charge.
When charges are fired under these conditions they are very much more effective
than when they are employed in the usual manner, that is to say, when they are
confined in the blasting hole simply by an ordinary tamping.
By the use of my charge holder or tamping trough its whole tensile strength is
applied to confine the gases generated by the explosion until they are able to find
a passage by rending the rock.
Having thus described the nature of my said invention and the manner of
performing the same I would have it understood that I claim the use in blasting
rock of a metal charge holder confining the charge longitudinally and thus resisting
by its tensile strength the escape of the gases generated by the explosion
substantially as described.
I also claim my tamping trough or charge holder substantially as described and
represented in the annexed Drawings.
In witness whereof I the said Herbert Newton Penrice have hereunto set my
hand and seal this thirteenth day of November in the year of our Lord One
thousand eight hundred and eighty three.
HN. PENRICE.
4.5.