Improvements in Machines for Planing or Dressing Slates.
Year: 1886

page_text: Date of Application, 28th Dec., 1886.
Specification Accepted, 8th Feb., 1887.
[Communicated from abroad by FRANCIS SHENTON, of Slatedale, County of Lehigh,
State of Pennsylvania, United States of America, Gentleman.]
Improvements in Machines for Planing or Dressing Slates.
I, WILLIAM PHILLIPS THOMPSON, Fel. Inst. P.A. of the Agency for Foreign
Patent Solicitors, 6 Lord Street, Liverpool, in the County of Lancaster, and 323 High
Holborn, in the County of Middlesex, 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:—
In
This invention relates to a method and means for shaving or planing the surfaces of
slates used for schools, counting houses, roofing and for other like purposes.
finishing slates for the purposes above mentioned it is necessary that they shall be
dressed to a uniform or substantially uniform thickness and rendered as smooth as
possible on both surfaces.
In practice it is found that the sheets or laminae of slate as they come from the
quarry are not only rough or irregular upon the surface but are frequently to some
extent curved or twisted, this twist or curvature from a plane being commonly of an
extent as great or greater than the thickness which is to be given to the finished slate.
Owing to this fact it is manifestly impossible to dress a thin slate twisted to this extent
in such manner as to produce plain surfaces of both sides so for the reason that in so
doing the slate would be cut through its entire thickness, or, in other words, would have
its entire substance removed at those points which depart to the greatest extent from
the plane of commencement. Hitherto many machines have been devised for dressing
slate, but so far as I am aware, they have each and all been designed to dress the surfaces
to a plane or dead level, on account of which, and of the reasons before mentioned, it
was impossible to employ them in connection with winding or twisting slates, unless the
latter were of very great thickness, so that a very large portion of the body would be
removed as waste in order to bring the remainder to a true flat form, an operation
which for economic reasons is inadmissible. Experience has shown that any attempt to
reduce twisted or irregular slate to a flat form by the action of cutting blades resulta
in a disintegration and loosening of the constituent laminae in such manner that the
slates present rough surfaces and soon become fractured.

page_text: Now it is a fact that for the purpose in view it is not necessary that the finished
slate shall have surfaces which are true planes. The essential requirement is that the
body of the slate shall be of uniform thickness and the two surfaces smooth, and it is
immaterial whether or not the surfaces are curved or twisted, within moderate limits.
In practicing the invention, I propose when necessary to take advantage of the fact
that the slates may be finished in a twisted or curved form, and I construct the machine
for carrying the invention into practice in such manner that the parts may adjust
themselves to the winding or twisting form of the slate. Consequently I am enabled
to take a thin twisted sheet of slate from which it would be impossible to produce a
merchantable sheet by the methods hitherto practiced and dress the same on its two
surfaces so as to produce a merchantable article. In this manner I am enabled not
only to utilize what would otherwise be waste material, but to avoid the labor and
expense of removing a large amount of surplus material.
The production of a finished surface which follows approximately the original
surface of the slate whether straight or curved is advantageous not only for the reasons
above mentioned but also because it is found in practice that smoother and more
satisfactory surfaces are produced.
With the ends above mentioned in view the invention relates to a mechanism for
passing a slate between the parallel edges of two knives permitting it meanwhile to
serve as its own guide, or, in other words, to follow the natural course due to its shape
or cleavage instead of compelling it to move in a fixed path as heretofore.
It further relates to the combination with two parallel knives of a pressure device
adapted to cause the passage of the slate between them without definitely limiting the
course of movement of said slate.
It further relates to an improved manner of sustaining the knives so that they may
be removed and replaced by others without stopping the action of the remaining parts
of the machine.
It also relates to means for adjusting the distance between the knives to compensate
for wear and to produce slates of different thickness.
It also relates to various details of minor importance which will be hereinafter
described and claimed.
Referring to the accompanying drawings,-
Fig. 1 represents a front elevation of a machine constructed in accordance with
this plan.
Fig. 2 is a sido elevation of the same.
Fig. 3 represents a vertical transverse section through one side of the machine on
the line y-y of Figs. 1 and 4.
Fig. 4 represents a horizontal section on the line - of Fig. 3, looking in a down-
ward direction.
Fig. 5 is an end elevation of the knives and the heads by which they are supported
detached, from the machine.
Fig. is a perspective view of the knives, their supports, and, in part, of the devices
in which the knives are adjusted and confined while in action.
Fig. 7 is a transverse vertical soction on a plane between the edges of the two
cooperating knives as indicated by the line a¹, a', Figs. 3 and 4.
The drawings represent a double machine or a machine containing two complete
dressing mechanisms located on opposite sides and operating independently of each
other. As these mechanisms are constructed in duplicate and are alike in their mode
of action the detailed description of one will apply equally well to the other.
In order that the essential characteristics of the machine may be the more readily
understood I will first describe one of the dressing mechanisms and subsequently the
devices by which motion is imparted thereto.
Each mechanism consists essentially of two fixed knives A, and A', having straight
or flat edges arranged parallel with each other and at a distance apart equal to the
thickness which is to be given the finished slate, and of a reciprocating pressure
device B, designed to act against one end or edge of the slate and force the same
longitudinally between the two.knives,

page_text: As represented in Figs. 3 to 7, the knives are inclined upward and inward in cross
section toward each other, their inner cutting faces being vertical, or approximately
so, while their upper and outer surfaces incline downward and backward so that the
material removed from the body of the slate will be discharged over them.
The pressure device B, consists preferably of a bar or plate slightly grooved or
recessed in its under edge to fit over and retain the edge of the slate while forcing the
same between the knives.
It is to be noted as an important-feature of this machine that this pressure device is
the only guide other than the knives themselves for the slate.
It is further to be noted that while the pressure device is acting on one end of the
slate to force the same between the knives the slate is free to move sidewise except as
it is guided by the latter. In consequence of this arrangement a curved or twisted
slate is permitted while passing through the knives to follow a curved or irregular
path corresponding to its curvature, whereby the knives are prevented from removing
an excess of material, or from cutting through the slate as would be the case were the
slate guided at both ends and compelled to move in a right line. A curved slate forced
between the knives by the device acting at one end, the opposite end being left free to
move, will emerge from the knives of a uniform thickness and with smooth surfaces,
retaining, however, the general form of curvature which it originally possessed. It
will, of course, be understood that it is not designed to employ slates which have an
excessive curvature, and further that straight or flat slates are preferred in all cases.
Referring now to the details of the mechanism by which the knives are supported
and adjusted, it will be seen on reference to Figs. 3 to 7, that the knives consist of
thin blades or sheets secured respectively to head blocks or supports D and D¹, each
block consisting of two upright end plates united by a transverse plate having an
inclination corresponding with the angle at which the knife is to be placed. The two
knives are arranged with their edges directly opposite to and parallel with each other
in the manner represented. In order to prevent the knives from being tipped forward
or inward by the strain applied to their cutting edges, each of the supporting blocks is
provided with projections or feet a, extending forward in advance of the knife in the
manner plainly represented in Figs. 5 and 6. In this manner the blocks are given a
broad base or support extending both in front and in rear of the cutting edge so that
there is no danger whatever, of the knife tipping either forward or backward when in
use. The head blocks are drawn together to bring the knives in a proper proximity
to each other by means which will be presently described. In order to effect their
automatic separation when released from the action of said devices, I propose to apply
springs in any other suitable manner, a convenient mode of application being that
represented in Figs. 4, 5, and 6, in which it will be perceived that one of the blocks
is provided with projecting fingers or tenons b, designed to enter corresponding holes
in the opposite block and bearing spiral springs c, which act between the two blocks
and tend to urge them apart. These tenons also serve the additional purpose of
guides to assist in maintaining the blocks and knives in the proper relations to each
other.
Referring now to the frame of the machine and to the means which cooperate with
the knives, attention is directed to Figs. 1 to 4. An upright rigid frame E, is
constructed in any form and of any material which will admit of its sustaining the
other parts. At the front of this frame are bolted firmly on opposite sides two
upright plates F, which are connected by cross-bars or slates G, and which have
upon their inner faces horizontal shoulders or ledges H. On these ledges the head
blocks supporting the two knives are seated, the knives receiving in this manner a
perfectly solid support. The knife bearing heads being thus supported it is necessary
that they shall be confined in position against lateral displacement and held at the
proper proximity to each other so that they may not be forced apart by the passage
of the slate between them. For this purpose I make use of two vertically sliding
plates K. These plates are arranged to slide in vertical guides or rests formed in
the stationary plate F, and are each provided at the front and rear edges respectively
with shoulders or flanges d, designed to engage over the other edges of the knife

page_text: bearing heads in the manner represented in Figs. 3 and 4, to prevent said heads
from moving apart. The two shoulders d, of each plate have a slight divergence
toward the lower ends, and the outer edges of the respective heads D, and D¹
are inclined to correspond, so that as the plate K, is depressed, its flanges act with
a wedging or contracting effect to draw the two heads D, and D', together, and thus
bring the edges of the two knives nearer each other. On the contrary the elevation
of the plate K, will have the effect of releasing the heads and permitting the knives
to be separated by the action of the springs before described. The vertical move-
ment of the two plates K, is secured by providing them with downwardly
extending arms or rack bars with spur teeth thereon as shown at e, Figs. 1, 3
and 7, and in arranging in connection with said rack bars operating pinions f
mounted on opposite ends of a horizontal shaft g, supported in fixed bearings.
By turning this shaft the two plates K, may be raised and lowered and the
distance between the knives thus adjusted with great precision. The weight of
the plates K, will cause them to move downward and draw the knives together
whenever they are released. To effect the proper adjustment it is only necessary,
therefore, to provide means for raising and sustaining the plates. A simple means
to this end consists in winding about a drum or pulley on one end of the shaft g;
a cord or chain h, the free end of which is connected to a screw, passed through
a fixed guide k, on the upper end. The nut and chain serve to limit the rotation of
the shaft and pinions in one direction and thus to sustain the plates K. By turning
the nut in one direction or the other the shaft will be caused to raise or lower the
plates and thus to vary the distance between the two knives as before explained.
The parts are so proportioned that by turning the shaft g, backward a sufficient
distance the flanges of the plate K, may be raised above and wholly out of engage-
ment with the knife supporting beads as represented in Fig. 6. The effect of this
action is to release the two heads so that they may be instantly withdrawn from the
machine in the event of the knives becoming dulled or broken.
Other heads bearing
knives in proper condition may be instantly substituted in place of those removed and
locked in position by permitting the plates K, to descend, and this, without stopping
the action of the other parts of the machine.
In operating with the machine it is proposed to construct a series of knife bearing
heads so that one set may be employed while the other is being sharpened or prepared
for use.
In order that the substitution of one head for another shall not cause the
variation in the thickness of the slate produced, and shall not require a special
adjustment of the parts, care is taken to adjust the cutting edges of the knives at
equal distances from the outer or rear edges of the supporting heads, these being the
edges against which the adjusting flanges d, engage. In order that the plates K
may be quickly elevated to release the cutting heads and retained in their elevated
position until the heads are removed and replaced by others, the shaft is provided
at one end with an operating lever or handle ¹ and also with a disk or wheel 1,
notched in its periphery to receive a pawl m, which is attached to the main frame and
which engages therein automatically when the shaft is turned to lift the plates.
Having thus described the knives and their adjuncts, attention is now directed to
the pressure devices. The bar of pressure device B, to which reference was before
made is secured to a vertically reciprocating head or slide L, which slides in fixed
guides M, bolted to the main frame. It is recommended that these guides be made
of metal and of a grooved form as shown, and that the edge of the reciprocating slide
be provided with wooden facings to work in said guides, it being found that the parts
thus constructed work in the presence of the dust arising from the operations in a
better manner than metal surfaces acting one on the other. It is to be distinctly
understood, however, that the details of the reciprocating head and of the guides
therefor may be modified to any extent desired as they do not constitute an essential
part of the invention. The slide may be permitted a slight horizontal play in or
between the guides.
In order to facilitate the introduction of the slate in a proper position, that is to say,
with its upper edge directly beneath the pressure device, which is kept constantly in

page_text: motion, I provide the pivoted guide arm M', represented in Fig. 3. This arm is made
of angular form and pivoted in the main frame behind or in rear of the pressure
device. Its rear end is weighted to hang in a pendent position when released and its
opposite end made of such form and length that when the rear end is depressed, the
forward end will stand in line vertical with the pressure device as plainly represented
in Fig. 3. In this position the forward end serves as a stop against which to rest the
upper end of the slate in placing the same in position. As the pressure head
descends, it acts upon the guide, which swings upon its pivot and turns backward
out of the way as indicated by the dotted lines.
I have now described. the construction of the dressing mechanism on one side of the
machine, it being remembered that the mechanism on the opposite side is of similar
construction. Attention is next directed to the mechanism for imparting motion to
the pressure devices of the two mechanisms. Each of the reciprocating heads or
slides is provided with an upright rack-bar N, and these two rack bars are arranged
to engage with spur teeth formed on opposite ends of a vibrating sector plate or
walking beam O, which is mounted at its center on a horizontal rock-shaft P,
sustained in bearings on the top of the main frame.
It will be perceived that under this construction the vibration of the sector plate
will cause the two pressure devices to rise and fall alternately. Motion is imparted
to the vibrating plate by means of a pitman Q, at one end thereof connected at the
opposite end to a crank R, on one end of a horizontal shaft S, to which motion may
be imparted in any suitable manner.
In the drawings I have represented the crank-shaft as provided with a large gear
wheel T, which receives motion from a pinion U, mounted on a second horizontal
shaft which is provided with a driving pulley V, which will be connected by a belt
with a motor of any suitable character."
In order to adapt the machine for dressing slates of different lengths without loss
of motion, the pitman is connected to the crank by means of an adjustable bolt or
wrist pin extending through a slot in the crank pin as represented. By means of
these devices, the throw of the crank pin and consequently the movement of .the
pressure device may be increased or diminished at will. Inasmuch, however, as any
variation in the throw of the crank is accompanied by a corresponding variation in
the point to which the pressure device is depressed, it is necessary to provide a means
of adjusting the pressure device vertically with respect to its rack-bar. This is
accomplished by connecting the lower end of the rack bar to the reciprocating frame
or slide by means of bolts m, extended through vertical slots in the slide.as plainly
represented in Fig. 1.
I am aware that in wood working machinery wood has been guided and forced
between parallel straight knives and also that wood has been forced in a free condition
or without guides between two knives having parallel curved edges adapted to produce
respectively the convex and concave surfaces of barrel staves. To such combinations
neither of which can be practically operated with slate or applied for the purposes of
this machine, I lay no claim.
The inventor believes himself to be, however, the first to provide for the passage of
slate without definite guidance between knives having parallel straight edges, which
must be employed with slate because of its laminated structure and brittle character
to avoid splitting and fracturing the same.
Having now particularly described and ascertained the nature of the said invention,
and in what manner the same is to be performed as communicated to me by my
foreign correspondent, I declare that what I claim is :-
1. In a machine for dressing slate, two opposing knives with straight parallel edges,
in combination with a pressure device arranged to reciprocate to and from the
knives, said parts operating as described independently of guides or other means for
determining the course of the slate; whereby the slate is given flat parallel surfaces
and the knives permitted to follow the course of its lamination,

page_text: 2. In combination with the pressure device to advance the slate, the two movable
head blocks provided with parallel knives, the stationary support for said head block,
and the movable locking plates, as described, engaging and confining the head blocks
to prevent their separation.
3. The combination of the movable head blocks provided with knives, the supports
whereon the heads slide, and the movable plates K, provided with the projecting
flanges engaging the heads whereby the heads may be confined and adjusted to
change the distance between the knives.
4. The knife supporting heads movable to and from each other, and the gravitating
plates K, provided with inclined flanges to approximate the heads and knives and also
with the rack-bars extending therefrom, in combination with the shaft and its
pinions engaging said bars; whereby the two plates K, may be raised and lowered
simultaneously and equally.
5: In combination with the movable knife supporting heads and the spring to
separate the same, the movable plates K, provided with the projecting flanges to
confine and adjust the heads, and means substantially as described for raising and
lowering said plates; whereby the distance between the knives may be varied at will.
6. In combination with the two inclined opposing knives, the supporting heads
therefor, having their bases extended forward in advance of the knives substantially
as described and shown, whereby the knives are prevented from tipping forward or
inward when in action.
7. In combination with the opposing inclined knives, the movable supporting heads
having the forwardly extended overlapping bases or feet u.
8. In combination with the solid head blocks provided with knives, the adjusting
plates K, engaging the head blocks as described, the racks and the shaft and pinions
to elevate said plates, the chain, having one end connected with the shaft and the
opposite end adjustably secured to the frame; whereby the adjustment of the chain
is caused to limit the descent of the plates K, and the consequent approximation of
the knives.
9. In a slate dressing machine, the combination of the two pairs of dressing knives,
the two vertically reciprocating pressure devices, their bars and the vibratory plate
connecting them; whereby the pressure devices are reciprocated alternately and the
dressing of the slates in vertical position permitted.
10. The dressing knives and the reciprocating pressure device, the rack bar
adjustably secured to the pressure device, the vibrating plate applied to operate said
rack bar, the pitman and the operating crank for the pitman adjustably connected
thereto whereby the stroke of the pressure device may be increased or diminished
to adapt the machine for dressing slates of different lengths.
WM. P. THOMPSON & Co.,
Agents for the Applicant.