AN IMPROVED SLIDE-VALVE FOR STEAM ENGINES
Year: 1883

page_text: LETTERS PATENT to Hermann Howaldt of Dietrichsdorf Dear Kiel Kingdom
of Prussia German Empire, Engineer for an Invention of " AN IMPROVED
SLIDE-VALVE FOR STEAM ENGINES
"
PROVISIONAL SPECIFICATION left by the said Hermann Howaldt at the
Office of the Commissioners of Patents on the 31st December 1883.
HERMANN HOWALDT of Dietrichsdorf near Kiel, Kingdom of Prussia German
Empire Engineer "AN IMPROVED SLIDE-VALVE FOR STEAM-ENGINES
"
The object of the invention is by the peculiar construction of the slide-valve for
steam-engines to reduce the friction between the working faces of the valve and of
the slide-faces of the chest-lid and of the cylinder, and to provide means for
balancing it against one sided steam pressure.
The invention is applicable to slide valves of single-cylinder steam-engines as
well as of common twin-engines, or of Woolf and compound-engines.
The slide-valve for a single-cylinder steam-engine forms a prismatic body of
trapezoid shaped cross section, which is provided with the necessary passages for
the steam, and which is made to slide up and down, or fore and aft upon the
valve-face of the cylinder in the well known manner. Its back face works along
the inner face of the steam-chest-lid. To prevent the slide-valve from being forced
by the steam, pressing upon the broader length-side, too tightly between the
convergent faces of the chest-lid and the cylinder, it is set by an adjustable plate
or strip, extending along its smaller length-side in such a manner that it works
freely and with the minimum of friction, at the same time tightly enough to
prevent the steam from entering between the working faces.
The adjustment of the before mentioned set-plate or strip may be effected in any
convenient and suitable manner, by screw, wedge, parallelogram or the like
movement. If the ports of the cylinder and the steam passages of the face of the
slide-valve are large it is advisable to provide a proportionate length groove on
the back-face of the slide-valve to create an opposite steam pressure. When
carefully constructed these opposite pressures will practically balance each other.

page_text: Or a recess of proportionate extent provided on the back-face of the slide-valve
may be connected with the exhaust or the condenser to produce the same effect.
In twin cylinders for common, Woolf-or compound and other engines lying or
standing alongside of each other, the slide faces of these cylinders are parallel in
axial direction but inclined or converging in the other. The correspondingly
trapezoid shaped slide-valve works between these cylinder-slide-faces. The steam
chest belongs jointly to both cylinders. The slide-valve is set as above described
by an adjustable strip or plate, working against the narrower length-side of the
slide-valve.
For greater security and for steadying the slide-valve a similar adjustable strip
or plate may be arranged against the wider length-side of the slide-valve. Where
a second slide is used for the cut off, together with a slide-valve for the distribution
of the steam one of them may be of parallelogram shaped cross section and the
other of a trapezoid shaped one, or both may.have the latter cross section.
The dimensions and the construction in other respects of the slide valve depend
upon the construction and kind of the engine to which it is to be applied. But
any experienced engineer will understand how to make this new slide valve
answer to any requirement by alterations not leaving the limits of the invention.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Hermann Howaldt in the Patent Office on the 30th June 1884.
HERMANN HOWALDT of Dietrichsdorf near Kiel, Kingdom of Prussia, German
Empire, Engineer. AN IMPROVED SLIDE-VALVE FOR STEAM ENGINES
"
The object of the invention is by the peculiar construction of the slide-valve
for steam engines to reduce the friction between the working faces of the slide
valve and the slide-faces of the cylinder and of the chest-lid and to provide means
for balancing it against one-sided steam pressure
The invention is applicable to slide valves of single-cylinder steam engines as
well as of common twin-engines or of Woolf-and Compound-engines.
In the accompanying Drawing Figures 1 to 3° represent a slide valve a of
the D-slide type of a common steam engine with one cylinder in various sectional
views-This slide valve a forms a prismatic body of trapezoid-shaped cross section,
provided with the passages necessary for the steam and which is made by any
valve gear not shown in the drawing, to slide up and down or fore and aft as the
case may be, upon the valve-face of the cylinder O and of that of the lid D of the
steam chest. Supposing the face d of the slide valve a to be uninterrupted and
full; the fresh steam could not pass at all upon the slide valve a whilst the
underside c would receive only a slight pressure with the tendency to lift the
slide valve a from the slide face of the cylinder C. To counterbalance this pressure
a recess or recesses extending lengthwise on the upper face d of the slide valve a
and of proportionate width are provided as shown in Figures 1. 2. 3 to allow a
partial pressure of the fresh steam to act upon this portion of the upper face d of
the slide valve a. The same effect is attained by providing a communication
between the exhaust or the condenser of the engine and an excavation on the upper
face d of the slide valve a, see Figure 1°.
To prevent the slide valve a being forced by the steam pressure upon the broader
length side h too tightly between the convergent faces of the lid D and the slide
face of the cylinder C it is set by an adjustable plate or strip fextending along its
smaller length side g in such a manner that it works freely and with the minimum
of friction, at the same time tightly enough to prevent the steam from entering
between the working faces. For greater security and for steadying the slide
valve a an adjustable strip or plate f, similar to that above mentioned can be
arranged to work against the broader length side h of the slide valve a.
The adjustment of the set plate or strip f may be effected in any convenient and
suitable manner by screws as represented on the right hand side of Figure 3-by
wedges f' manipulated by screws and nuts as represented on the left hand side of
Figure 3. on top of Figure 2 and in Figure 3º, or by other devices which would
answer the purpose-The wear and tear of the working faces g. h of the slide
valve a and of the plates fare compensated by re-adjusting the plates f
The new trapezoid slide valve is exceedingly well adapted for twin cylinders
of common, Woolf or Compound or other engines, as it works steam tight upon
the slide faces of each of the two cylinders and at the same time with a minimum
of friction.
As an example-in Figures 4 and 5 are shown the two cylinders of a Woolf
Engine with the new trapezoid slide valve a arranged between the slide faces of
the cylinders I and II which faces are parallel in axial direction but inclined or
converging in the other, corresponding to the converging faces of the slide
valve a-
The steam chest belongs jointly to both cylinders I and II. The slide
valve a is set by an adjustable strip or plate ƒ working against the narrower length

page_text: side g of the slide valve a-A collateral strip fis provided against the broader
length side h. fi represents the cross section of the wedges by means of which the
set plates fare adjusted.
Where a second slide a' for the cut-off is used on top of the slide valve a for the
distribution of the steam one of them may be of parallelogram-shaped cross section
and the other of trapezoid shape in which case the working faces of the chest-
lid and of the cylinder or those of two cylinders become converging-Or the
cross section of both slide valves a and a¹ may be a trapezoid in which case the
steam chest is of rectangular cross section as represented in Figure 6.
The dimensions and the construction in other respects of the slide valve depend
upon the construction and kind of the engine to which it is to be applied. But any
experienced engineer will understand how to make (by alterations not leaving
the limits of the invention) this new trapezoid slide valve answer to any
requirement
Having now particularly described the nature of my said invention and the
manner of carrying the same into effect I would have it understood that what
I claim is,
First. A slide valve a for steam engines the cross section of which irrespective of
the required steam passages is a trapezoid which works between the slide face of
the cylinder C and that of the lid D of the steam chest. or between the slide faces
of two cylinders I, II-and which can be adjusted by means of an adjustable set
plate or strip for by two such adjustable set plates in such manner that the slide
valve a will work freely steam tight and with a minimum of friction substantially
as herein shown and described and for the purpose explained
Second In combination with a trapezoid slide valve a for steam engines, one or
more adjustable set plates f substantially as herein shown and described and for
the purpose explained.
In witness whereof I the said Hermann Howaldt have hereunto set my hand
and seal this tenth. day of June One thousand eight hundred and eighty four.
HELDMANN HOWATTT
11