Improvements in Pneumatic Hammers for Hand Use.
Year: 1899

page_text: Date of Application, 24th Oct., 1899-Accepted, 13th Jan., 1900
COMPLETE SPECIFICATION (AMENDED).
Improvements in Pneumatic Hammers for Hand Use.
I, JOSEPH BOYER, of 5334, Maple Avenue, Saint Louis, in the State of Missouri,
United States of America, Manufacturer, do hereby declare the nature of this inven
tion and in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement :-
My invention relates more particularly to that class of tools, commonly known as
pneumatic hammers, in which a reciprocating piston operates as a hammer or striker
to deliver blows upon a chisel or other working tool inserted in or carried by the
front end of the cylinder; and it has for its principal object the provision of means
whereby the piston may be permitted a longer stroke, and thereby enabled to strike
a harder blow, than has heretofore been usual in devices of this character. This I
accomplish in the manner and by the means hereinafter described by reference to
the accompanying drawings, in which Figure 1 represents a middle longitudinal
section of a pneumatic hammer embodying my invention and equipped for opera-
tion as a riveter or riveting hammer; Figure 2 an enlarged detail view similar to
Figure 1 with the rear end of the structure, and also a portion of its middle, broken
away to accomodate the view to the length of the sheet, and showing the piston at
the front end of its stroke; Figure 3 a middle longitudinal section on the line 3-3
of Figure 2; and Figure 4 a perspective view of the spring-clip for holding the
rivet-set in place.
The same letters-of-reference are used to designate corresponding parts in the
several views.
My invention has been illustrated in the accompanying drawings as embodied in a
hand riveting tool, and the cylindrical body or barrel A of the tool has secured to
its rear end the usual grasping handle B through which extends an inlet passage C
for the motive fluid, controlled by a throttle-valve located within the handle B and
operated by the thumb-lever D, Figure 1. Screwed upon the front end of the
cylinder A is a cap or nose-piece E having a central bore which receives the stem or
shank of the riveting tool F. the latter in the present instance being detachably
connected to the piece E and held from displacement by a spring-clip G₁G.
Fitted within the cylindrical bore of the body A of the tool is a long bushing or
sleeve H, whose internal bore constitutes the piston-chamber within which recipro-
cates the piston I. This sleeve is held in place by pins (not shown) driven through
it and the cylinder A and by a flat ring J clamped between the front end of the
cylinder and an internal annular shoulder on the cap E.
Beyond the rear end of the sleeve or bushing H the cylinder A is bored out to
form a chamber 1, and has inserted in its rear end a flanged bushing M, the internal
bore of whose central tubular portion M¹ constitutes the extreme rear end of the
piston-chamber and receives the piston I at the end of the rearward stroke of the
latter

page_text: The flanged rear portion of the bushing M. has a series of holes N bored through it,
which holes communicate at their forward ends with the chamber L and at their
rear ends with a circumferential groove 0 formed in the handle-base or cylinder-
head P, said groove communicating with the inlet passage C in the handle B as usual,
so that whenever the throttle-valve in the handle is opened by depressing the thumb-
lever D the supply of motive fluid will be admitted to the chamber L.
Mounted to slide forward and backward upon the central tubular portion M¹ of the
bushing M is a sleeve Q provided at its forward end with an outwardly projecting
flange against which bears the front end of a coiled spring R which surrounds the
sleeve and at its rear end is seated in a circumferential recess S in the bushing M.
This sleeve Q constitutes a second throttle-valve, independent of that within the
handle B, for controlling admission of the motive fluid to the tool, as hereinafter
more fully described. The spring R presses the sleeve Q forward and normally holds
it in the position shown in Figure 3, in which position its flanged forward end seats
within a circumferential groove U formed around the front end of the sleeve H
(between the latter and the wall of the cylinder A), while the body of the sleeve
covers a groove or annular space T between the rear end of the bushing H and front
end of the portion M¹ of the bushing M, and cuts off communication between the
chamber L and interior of the piston chamber through said groove T. For the
purposes of description at the present point the sleeve Q may be assumed to be
forced rearward to the position shown in Figures 1 and 2, thereby uncovering the
groove T.
Communication between the motive fluid supply (in the chamber L) and the rear
end of the piston chamber through the groove T is further controlled by a valve (or
rear half of a two-part valve) V, located in an annular chamber formed for it in the
rear end of the bushing H and extreme forward end of the bushing M¹. When slid
to rearward or left-hand position, Figure 2, the valve V covers the groove T and cute
off communication between the motive fluid supply and the rear end of the piston
chamber, and when slid to forward or right-hand position, Figure 1, it uncovers the
groove T and permits the motive fluid to pass from the chamber I, to the rear end
of the piston chamber (assuming the throttle-valve Q to be forced rearward to the
position shown in Figures 1 and 2). The front or right-hand end of the valve V
co-operates with an annular groove W and controls cominunication of the piston-
chamber (through said groove) with the exhaust openings X for the rear end of the
piston-chamber. When the valve V is in forward position, Figure 1, it covers the
groove
W and cuts off communication with the exhaust, and when it is moved rear-
ward, Figure 2, it uncovers said groove and opens communication with the exhaust.
Located in the forward end of the piston-chamber, in a suitable chamber formed
to receive it, is a second similar valve (or forward half of the two-part valve) V1,
whose forward end controls an inlet groove T¹ through which the motive
fluid is admitted to the front end of the piston-chamber, and whose rear end controls
an exhaust groove W¹ communicated with the exhaust outlets X¹ for the front end
of the piston chamber. Motive fluid is conveyed from the source of supply to inlet
groove T¹ through two passages YY (dotted lines Figures 1 and 2, and full lines
Figure 3), extending longitudinally of the cylinder A and communicating at their
rear ends with the circumferential groove or recess U surrounding the rear end of
the bushing H and in open communication with the chamber L, Figure 2.
Whenever the valve Q is pressed rearward to the position shown in Figures 1 and 2
the motive fluid will pass from the chamber L through the passages Y Y to the
groove T, and thence through said groove (when the position of the valve V1 permits)
to the front end of the piston chamber.
The particular shape of the valves V and V1 is not essential, and instead of the
shape shown they may, for instance, consist of plain rings or sleeves of uniform thick-
ness throughout, the only requirement being that the valve V shall present (in some
form) a rearwardly facing pressure area to be acted upon by the air pressure as here-
inafter described, and the valve V₁ a forwardly facing pressure area for the same
purpose. In the present instance the valves have been shaped as shown in the

page_text: drawings chiefly for the purpose of decreasing their weight, and the pressure area of
the valve V consists both of the rear end of the valve and the annular shoulder
formed at the rear end of its contracted middle portion, while the pressure area of the
valve V¹ consists of its forward end and the annular shoulder formned at the front end
of its contracted middle portion.
The two valves V V1 (or the two parts of the single valve, if it be so considered)
are connected by or have interposed between them two small rods or wires A¹ A¹
extending longitudinally through the cylinder wall from one end to the other, so that
when the valve V1 moves rearward its movement will be communicated to the valve V
and move the latter rearward, and when the valve V is then moved forward it will
communicate its movement to the valve VI and move the latter forward. The rods
or wires A¹ A¹ are not in the present instance attached at either end to the valves,
although the operation of the parts would not be materially different if they are were.
The internal bores of the valves V and V1 are of such size as to snugly fit the
piston I when the latter enters the valves at the opposite ends of its strokes, and
under the conditions above described, when the piston approaches the forward end of
its stroke, for instance, and enters the valve V₁ it cuts off the portion of the piston
chamber in front of said valve from communication with the groove W₁ and
exhaust ports X¹. During this further forward movement, therefore, the air thus
trapped in front of the piston will be compressed, and acting upon the forward end or
pressure area of the valve V¹, will force the valve rearward, as in Figure 2, thereby
closing the exhaust groove W¹ and uncovering the live-air groove T¹.
The rearward movement of the valve V₁ to the position shown in Figure 2 will,
through the instrumentality of the rods or wires A¹ A¹, have moved the valve V at the
rear end of the piston-chamber to its rearward position, thereby cutting off the inlet
of the motive fluid to the rear end of the piston-chamber, and opening the rear end
of the piston-chamber to the exhaust through the groove W and exhaust ports X.
It will be understood that the piston, at its forward stroke, is not arrested by the
air confined in front of it after it enters the valve V1, as, before explained, but that on
the contrary the piston continues its forward movement and delivers its blow to the
riveting tool F as in Figure 2. In completing such forward movement the front end
of the piston passes through a loose bushing or sleeve B¹ fitted to slide backward and
forward in a chamber within the cap E at the front end of the cylinder A, for a pur-
pose hereafter described. The sleeve B¹ in the present instance is provided with
several internal longitudinal grooves to permit the air in front of the piston to pass
backward and not form a cushion between the piston and shank of the rivet-set F.
The rebound of the piston from the blow delivered by it to the riveting tool
(the latter being pressed firmly against the end of the rivet) will start the piston
backward and its further movement will be effected by the motive fluid admitted in
front of it through the inlet groove T¹ which has been uncovered by the rearward
movement of the valve V¹. At the end of its backward movement the piston passes
entirely through the valve V and enters the internal bore of the bushing M, which it
snugly fits, so that the air in said bushing is trapped behind the piston and then com-
pressed, and cushions the piston and starts it forward again, and when its rear end
passes forward out of the bushing M the supply of motive fluid is admitted behind it
through the groove T (now uncovered by the forward movement of the valve V) to
drive it forward for its next, blow.
Abutting against the rear face of the loose sleeve B' are the forward ends of two
rods D¹ extending rearwardly through the passages Y Y heretofore referred to, and
abutting at their rear ends against the flanged forward end of the cylindrical throttle-
valve Q heretofore described, Figure 3. The coiled spring R presses the valve Q
forward, and, through the medium of the rods D¹, presses the sleeve B¹ and riveting
tool F forward and normally holds them in the position shown in Figure 3, in which
position the valve Q covers both the groove T and the rear ends of the passages Y Y
and cuts off the supply of the motive fluid from both ends of the piston chamber,
even if the throttle-valve in the handle of the tool be open. When, however, the
rivet-set F is applied to the end of the rivet and the whole tool forced forward and

page_text: the set pressed firmly against the rivet, the body of the tool will be forced forward
upon the shank of the rivet-set and the sleeve B¹, rods D¹, and valve Q will be forced
rearwardly within the tool, causing the valveQ to uncover the groove Tand passages YY,
to admit the motive fluid to the opposite ends of the piston-chamber. In this
manner and by these means the motive fluid is not only automatically admitted to
the tool by the act of pressing the latter up to its work, but the tool is in-operative
unless it is pressed against the work. This provision for preventing operation of the
tool except when pressed to its work is of importance, since otherwise the tool might
be run without the presence of anything to resist the powerful blows of the long-
stroke piston, with the result that such blows would be liable to knock off the entire
front end of the tool.
For the purpose of connecting the rivet-set to the body of the tool and permitting
its ready detachment when desired the spring-clip G shown in Figure is
provided. It is cut away at one side and provided at its opposite ends with internal
flanges engaging respectively an annular shoulder upon the front end of the cap or
nose-piece E and a corresponding annular shoulder upon the rivet-set F. When
the set is to be removed from or inserted into the tool the ends of the clip G' are
sprung apart with a pair of suitable pliers, whereupon the shoulder upon the set may
readily pass the flanges upon the clip as the set is withdrawn or inserted.
As will be understood from the foregoing description and explanation of my inven-
tion, the length of the stroke of the piston is not in anyway limited by the length of
the piston itself, but, on the contrary, the piston may be given any desired length of
stroke, even many times its own length. It is therefore possible by the employment
of my invention to increase the length of the stroke of the piston of pneumatic
hammers to any degree desired, without increasing the lengths of the pistons them-
selves, and consequently by simply increasing the length of the cylinder and piston-
chamber the length of the stroke of the piston and consequent force of its blow may
be correspondingly increased without otherwise increasing the size or adding to the
weight of the tool.
It is a desideratum in pneumatic tools for many classes of work to obtain as
powerful a blow of piston as possible with minimum length of tool.
By the
employment of my invention the power of a tool of given length may be increased
by shortening the piston (within certain limits) and thereby increasing the length of
its stroke although decreasing its weight; while by lengthening such tools, but still
confining them within reasonable limits as to length, a force of blow may be
obtained far beyond anything heretofore known in tools of this character.
The foregoing description and explanation of the particular embodiment of my
invention illustrated in the drawings has necessarily involved reference to many
details of construction, but it will be understood that my invention, in its broader
scope, does not relate to details of construction, but contemplates broadly the novel
mode of operation described and appropriate means for carrying it out, as will be
indicated by the several claims setting forth my invention.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what I
claim is
1. A pneumatic hammer-comprising-a-cylinder,-a-hemmering-piston located
therein and having a length of stroke-greater-than--its own length, and valve
mechanism controlling suitable inlet and exhaust passages to produce reciprocations
of the piston.
2.1. A pneumatic hammer comprising a cylinder, a hammering piston located
therein and having a length of stroke greater than its own length, and a valve
operated by air compressed by the piston and controlling suitable inlet and exhaust
passages to produce reciprocations of the piston substantially as described and
illustrated.
9. 2. A pneumatic hammer comprising a cylinder, a piston therein, and a valve
composed of two co-operating annular portions or rings located in opposite ends of

page_text: the piston-chamber and operated by air compressed by the piston and controlling
suitable inlet and exhaust passages to produce reciprocations of the piston.
1. 3. A pneumatic hammer comprising a cylinder, a piston therein, and a valve
composed of two annular portions or rings located in the opposite ends of the piston-
chamber and operated by air compressed by the piston, and connected by rods passing
longitudinally through the cylinder wall.
144. In a pneumatic hammer, the combination of a valve composed of two co-
operating annular portions or rings located in opposite ends of the piston chamber,
and a piston passing through said valve rings at the opposite ends of its strokes
and shifting them in a direction opposite to its own movement, by means of the air
compressed in front of it.
5. 22. In a pneumatic hammer having an annular inlet groove for the motive fluid,
the combination of a cylindrical throttle-valve for controlling said groove, a spring
normally pressing said valve forward in position to close the groove, a working tool
carried by the front end of the cylinder, and rods extending lodgitudinally through
the cylinder wall between said working tool and valve, for forcing said valve
backward and uncovering the inlet groove when the tool is pressed against its work
substantially as described and illustrated.
6. 23. The combination, with a pneumatic hammer and its removable working
tool F, of the spring-clip G₁ co-operating therewith in the manner and for the
purpose described.
21. The spring-coupling clip G-adapted-to-co-operate in the manner described
with-annular shoulders upon the two-members to be coupled together.
Date HD HOLay
COOL
1000000
HERBERT HADDAN & Co.,
Agents to Applicant, 18, Buckingham Street, Strand, W.C.