Improvements in Compound Engines, Applicable also to Percussive Boring Machines.
Year: 1889

page_text: Date of Application, 1st Mar., 1889
Complete Specification Left, 30th Nov., 1889-Accepted, 11th Jan., 1890
PROVISIONAL SPECIFICATION.
Improvements in Compound Engines, Applicable also to Percussive
Boring Machines.
I, AUGUST BERNHARDT DRAUTZ of Stuttgart, in the Empire of Germany, Civil
Engineer, do hereby declare the nature of this invention to be as follows:-
This invention relates to an improved compound engine with two pistons of
different cross section and one distribution port and has for its principal purpose
to obtain a more complete utilization of the motive power. The two pistons are
concentrically connected by means of a rod having a cross section inferior to that
of the small piston, while the piston rod passes through the rear cylinder-cover.
The pistons operate in two corresponding cylinders relatively connected by a
distribution port, the inlet opening of which terminates in the small cylinder about
the middle thereof, and, at the end of the return stroke, communicates with the inlet
for the fresh motive power, while, at the end of the forward stroke, it is situated
between the two pistons. The other aperture of the port terminates in the large
cylinder at the rear end thereof. The port for the exhaustion of the utilized motive
power is so provided as to be open between the two pistons at the end of the return
stroke and closed by the large piston at the end of the forward stroke.
The improved engine works as follows:
The fresh motive power arrives, when the pistons are situated at the end of their
return stroke, through the small cylinder and the distribution canal behind the rear
surface of the large piston and, owing to the different cross sections of the pistons,
drives them jointly forward notwithstanding the counter pressure produced by the
entering motive power. On the closing of one orifice of the distribution port by the
small piston, the enclosed motive power expands until the piston has passed and frees
said orifice. It is understood, that the volume of the distribution canal is so
measured, that the pressure on the rear surface of the large piston, at the end of the
forward stroke, still overcomes the constant pressure acting on the front surface of
the small piston.
At the end of the forward stroke, the two halves of the large cylinder are in
connection with each other through the distribution port, and the already expanded
motive power therefore is allowed to be distributed on the two surfaces of the large
piston and produce compensation of pressure with regard to the latter.
The constant pressure of the motive power on the small cylinder forces both
pistons backward, thereby closing the respective aperture of the distribution port
and producing further expansion in the spaces between the two pistons, while
compression takes place in the distribution canal and in the rear half of the large
cylinder. This second period of expansion terminates with the opening of the
exhaust port by the large piston, whilst simultaneously the compression ceases with
the opening of the respective orifice of the distribution port by the small piston. On
the arrival of the pistons at the end of the return stroke, the above operation is
repeated.
The improved system is particularly adapted for percussive boring machines to
allow the utilized motive power to be employed for removing the bore-dust. For
this purpose, the exhaust port above referred to is dispensed with and the piston rod,
leading to a hollow boring tool, is likewise made hollow and connected by means of
small apertures provided in the large piston with the cylinder spaces between the
two pistons. With this arrangement, a second period of expansion does not occur,

page_text: but the utilized motive power passes from the rear half of the large cylinder through
the distribution port and said apertures into the piston rod, whence it proceeds to the
hollow tool and to the bore-hole and expels the bore-dust from the latter.
Dated this 29th day of February 1889.
HUELSER & Co.,
Agents to Applicant.
COMPLETE SPECIFICATION.
Improvements in Compound Engines, Applicable also to Percussive
Boring Machines.
1, AUGUST BERNHARDT DRAUTZ of Stuttgart in the Kingdom of Wuerthemberg,
Empire of Germany Civil Engineer, 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 :-
The object of this invention is a motor for gaseous working fluid applicable as:
1) compound engine with two successive periods of expansion, 2) simple expansion
engine, and 3) percussive boring machine.
The engine as under 1) can be changed into an engine as under 2) by a mere
interchange of one piston and a single reversion of two cocks, or into an engine as
under 3) by simply removing a closing screw in the hollow piston rod. Consequently
the improved engine, without deviating from the principle of construction, can be
so made as to be applicable only as one of the three engines before mentioned.
Referring to the accompanying drawing, in the various figures of which like letters
denote analogous parts,
Fig. 1. is a longitudinal section of the main body of the improved engine so con-
structed as to be applicable only as a compound engine with two periods of expansion,
the piston being shown as having arrived at the end of the return stroke.
Fig. 2 is a longitudinal section of the main body of the improved engine, applicable
only as a simple expansion engine, the piston being shown as occupying the same
position as in Fig. 1.
Fig. 3 is a longitudinal section of the main body of the improved engine as
compound engine with two periods of expansion.
Fig. 4 a longitudinal section of the shown by Fig. 3, converted into a simple
expansion engine.
Fig. 5 is a section along line CC Fig. 3.
Fig. 8 a section along line Ę E Fig. 9.
Fig. 9 a section along line DD Fig. 3.
Fig. 6 represents the shorter, and
Fig. 7 the longer of the small pistons A¹.
The engine as shown by Figs. 3 and 4 essentially consists of the inlet muffle G,
the cylinder B B' closed in front by means of a cover, the piston rod a a¹, the large
piston A and the small piston A'. The cylinder B B' is provided with ports / h and
cocks R Fig. 9 and R Fig. 5. The piston A is situated on the fore (right) part a
of the piston rod a a¹ and operates in the fore part B of the cylinder B B', while
the rear piston A¹ is provided on the rear (left) part a' of the piston rod a a¹ and
moves in the rear (left) part B' of the cylinder B B¹.
;
The fresh motive power is admitted through the muffle G and when utilized
escapes through the hollow cock R. The latter has two apertures k¹ k², which so
communicate with two exhaust channels o' o³, provided in the large cylinder B as to
always allow one of said channels to be closed by the cock R. The channels o¹ o²
are so placed in cylinder B, as to cause one of the same, o², serving for the escape
with two periods of expansion, to be closed by the piston A on the termination of the
return stroke, and opened at the end of the forward stroke, while the second exhaust

page_text: channel o¹ is disclosed at the end of each of the strokes by the piston A, thereby
allowing of escape on each change of the piston.
When the improved engine is intended to operate as compound engine, the
cocks R and R¹ are given the position shewn in Fig. 3; the port h is in front
closed by cock R', the aperture o2 Fig. 8 in cylinder B is disclosed, the opening /²
in cock R having been placed thereover, and the piston A', represented by Fig. 7, is
employed. Now the engine will operate precisely as if it were built only as a
compound engine, this case being represented in Fig. 1.
The fresh motive fluid enters, when the piston is in its right-hand position, from G
through cylinder B¹ into channel h, passes to the rear (right) side of the
piston A and, owing to the difference of area in the cross section of the pistons,
drives A A¹ to the left, notwithstanding the constant counter pressure produced on
piston A¹ by the incessantly admitted motive fluid. As soon as piston A¹ has closed
the fore termination of channel the separated motive force enclosed in and B
expands until piston A' has passed and re-opens the mouth of channel Fig. 1.
The volume or capacity of the distribution channel h must of course be so
determined that the pressure on the right-hand surface of A still exceeds at the end
of the stroke the constant pressure on the left-hand surface of A¹. As soon as the
small piston has assumed the position shown in Fig. 1, communication is established
between the fore and rear half of cylinder B through channel h and compensation of
pressure takes place relative to piston A.
The pressure of the fresh motive force constantly operating on the left hand surface
of piston A¹ subsequently drives both pistons to the right. Thereby the fore mouth
of channel is closed and a further expansion occurs in the cylinder spaces comprised
between the pistons A and A', while, in the channel 7 and the rear cylinder space-
of B, compression is produced.
This second period of expansion on the opposite side of where the first took place
terminates with the uncovering of the exhaust port J (in the combined engine
Fig. 3 by the opening of the escape channels o2 and 2 in cylinder B and cock R
respectively) by the piston A. The compression terminates with the simultaneous
opening of the fore mouth of channel / through piston A¹.
When employing the engine as percussive boring machine the position of cocks R
and R' is the same as when using it as a compound engine as above described;
only the screws closing the hollow piston rod a in front (on the right) has to be
removed. The improved engine now operates as if it were constructed exclusively as
a percussion engine, the utilized motive power being in this case not employed for
producing a second period of expansion but for removing the bore dust. To this
end the piston rod a connected with a hollow boring tool is likewise hollow, and
brought in communication through small openings i provided in the large piston A
with the cylinder spaces comprised between the pistons A and A'. In this modifi-
cation the once expanded motive force flows from the right hand half of cylinder B
through channel h and openings i in piston A into the hollow piston rod a and hence
passes through the hollow boring tool to the bore hole freeing the same of the bore
dust. The hollow piston rod a in this case replaces the exhaust port J.
In order to employ the improved engine as a simple expansion enginé Fig. 4 the
piston represented by Fig. 7 is used. The cocks R and R' are given the position
indicated in Fig. 4; the inlet channel h¹ is opened by cock R' likewise the
opening o¹ Fig. 8 in cylinder B, the aperture ki in cock R having been placed
thereover, the piston rod a being closed by screw s. The engine now works
exactly as if constructed exclusively for one period of expansion, this case being
embodied in Fig. 2.
At the end of the left hand stroke Fig. 2 both apertures of channel h¹ are
uncovered, while that opening of channel h which terminates in cylinder B¹ is closed
by piston A¹. At the end of the right hand stroke the left hand mouths of channels h
and are opened while the right hand aperture h³ is closed by piston A¹. The
exhaust port is situated exactly in the middle of cylinder B so as to be half open

page_text: about the end of each stroke. The further operation of this simple expansion engine
is easily understood from the foregoing description, reference being had to Figs. 2
and 4.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, 1 declare, that what 1
-claim is :
1) A percussion engine for gaseous motive fluid, essentially consisting of a double
cylinder B B¹, provided with distribution ports h and h¹, which latter is adapted to
be closed by cock R', and outlet openings o¹ 02 adapted to be engaged or dis-
engaged by cock R, a double piston A A' provided on a piston rod a a¹, the piston
rod a being adapted to be closed in front and brought in communication through
apertures i in piston A with the space of the cylinder, an inlet muffle G, said engine
being applicable, by correspondingly adjusting the cocks R¹ and R and, when
required, removing the closing screws, either as a compound engine with two periods
of expansion or as a simple expansion engine or as percussion boring machine,
Figs. 3 to 9, substantially as set forth.
2) For the purpose of attaining complete utilization of the motive force the
combination of the various constituents of an engine with two periods of expansion
and a single distribution port / connecting the two cylinders B and B', said con-
stituents being so constructed and employed as to allow one expansion of the motive
force to take place during one stroke of the piston on one side, and a second
expansion of the already expanded motive force during the reverse stroke on the
other side of the piston substantially as set forth.
3) The combination of the various constituents of an engine in which the once
expanded motive force is not employed for producing a further, second, expansion,
but passes through suitable apertures i in piston A into the hollow piston rod a for
the purpose of allowing the utilized motive force to be employed for mechanically
removing the bore dust from the bore hole when the engine is employed as a
percussion boring machine, substantially as set forth.
4) The combination of the various constituents of an engine with one period of
expansion but two distribution ports h and h¹ which so connect the two cylinders B
and B' as to cause an expansion of the motive force to be produced, during one stroke
of the piston on one side and, during the reverse stroke on the other side of the
piston Fig. 2, substantially as illustrated and described.
Dated this 30th of November 1889.
A. B. DRAUTZ.
By Huelser & Co.,
Attorneys.