Note: Descriptions are shown in the official language in which they were submitted.
554
This is a division of commonly assigned copending
Canadian Application Serial No. 360,007 filed September 10, 1980.
BACXGROUND OF THE INVENTION
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While not limited thereto, the present invention is
particularly adapted for use in pneumatic rock drills of the
type in which a rotating drill rod is recriprocated by means of
a hammer piston which repeatedly strikes the end of the drill
rod opposite a drill bit~ In such drills, the hammer piston
delivers a blow upon the drill rod at one end of its.downward
stroke, the inital propulsion of the piston toward the rod
- being due to expansion of a fluid under pressure; while the
- final portion of the stroke is due to the inertia of the piston
and any.residual pres~ure in the cylinder after the fluid
pressure source has been cut off. Similarly, the upward stroke
of the hammer piston is initiated by fluid under pressure;
while the remainder of the upward stroke is due to the inertia
of the piston and/or any residual pres~ure in the cylinderO
In the past, many pneumatic motors of this type have
required a plurality of input ports extending through the wall
-of a cylinder which houses ~he hammer piston. This, however,
increases the cost of the assembly. Furthermore, prior art
designs as exemplified, for example, in U.S. Patent Nos. 873,9387
1,128,416, 1,660,201, 1,800,344, 2l748,750 and 3,329,068 have
been deficient in one respect or another as regards the
efficiency and cost of the pneumatic motor.
SUMMARY OF THE.I:NVENTION
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The pare:nt application, of which this is a division,
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relates to rock drills and the like for which there is provided
a pneumatic motor comprising a cylinder having a large diameter
portion communicating with a smaller diameter portion. A
hammer piston is reciprocable within the cylinder and has an
upper portion disposed within the large diameter portion of the
cylinder and a lower portion disposed within the small diameter
portion of the cylinder. A central bore extends through the
upper and lower portions of the piston; while a single input
port extends through the wall of the small-diameter portion of
the cylinder intermediate the ends of the smaller diameter
piston portion. This input port is adapted to communicate with
a reduced diameter area in the outer peripheral surface of the
lower portion of the piston, the reduced diameter area being out
of sliding engagement with the wall o~ the s~aller diamet~r portion of
the cylinder and being adapted in one position of the hammer
piston to connect the input port to a lower side of the upper
piston portion to force it in an upward direction. In a second
position of the hammer pistor., the input port is connected
through the central bore of the piston to the upper side of the
large diameter piston portion to force it in the opposite
direction.
One or more exhaust ports is provided in the cylinder
opposite the large diameter portion of the piston, the exhaust
ports being in communication with the central bore of the piston
when the inlet port is in communication through said reduced
diameter area with the lower side of the upper piston to force it
upwardly. On the other hand, when the inlet port is no longer
in communication with the lower side of the upper piston portion
during the upward stroke, the exhaust ports are then in communi
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cation with the same lower side of the upper piston portion. On the down-
ward stroke, air entering -through the inlet port under pressure passes
through the central bore of the piston ac-ting on its upper surface to force
it downwardly. After the piston has moved downwardly to the poiNt where
its upper surface is no longer connected to the inlet port, the expended
air passes out of the exhaust ports. The exhausted air ~hen passes through
a muffler surrounding the motor and having walls preferably formed from an
elastomer.
The invention of the present application is particularly directed
to the aforementioned muffler. Accordingly, the present invention may be
broadly coNsidered to provide, in a pneumatic motor having cylinder means,
a piston reciprocable within-the cylinder means, ports in the wall of the
cylinder through which exhaust gas passes, and a muffler surrounding the
cylinder for receiving the exhaust gas, the improvement in the muffler comr
prising: an annul æ wall of resilient material surrounding the cylinder
means, annular spacers separating the wall from the cylinder means, openings
in the spacers through which exhaust gas can pass, the openings in at least
some spacers being displaced about the cylinder axis with respect to the
opening in a next adjacent spacer, whereby exhaust air will, after passing
in a generally longitudinal direction with respect to ~e cylinder axis,
flow generally circumferentially to the next ~he: opening, and an opening
in the annular wall through which exhaust gas passes to the a~mosphere after
passing through the openings in the spacers.
The above and other features of the invention will become appar-
ent from the following detailed description taken in coNnection with the
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accompanying cross-sectional single figure drawing which iilustrates one embodi-ment of the invention.
With reference now to the drawing, the pneumatic motor shown
- comprises a cylinder 10 having a large diameter portion 11 which communicates
with a lower small diameter portion 12. Disposed on the inner periphery of the
smaU diameter portion 12 is a buffer ring 14 whieh, for purposes of the present
specification and the claims which follow, will be considered to be part of th~
lower portion 12 of the cylinder 10. Reciprocable within the upper and lower
portions 11 and 12 of the cylinder is a hammer piston 16 having an upper large
diameter portion 18 reciprocable within the upper large diameter portion 11 of the
cylinder 10 and a lower smaller diameter portion 20 reciprocable within the lower
smaU diameter portion 12. As shown, the piston portion 20 is reciprocable withinthe inner periphery of the buffer ring 14. The piston 16, as it reciprocates within
the upper and lower portions of the cylinder 10, is adapted to engage or strike a
tappet 22 which engages the upper end of a drill rod 24, thereby imparting a ;
reciprocating or striking motion to the drill rod 24 and a drill bit, not shown,carried at its other end. A motor, generally indicated by the reference numeral
26, is utilized to rotate the drill rod 24 about its axis. The motor 26 is one of a
number of different types which can be employed and forms no part of the
~0 present invention.
Formed in the wall of the small diameter portion 12 of the cylinder 10 is
an annular space 28 which3 in tum, communicates with a single irlet port 30.
- Threaded into port 30 is an ir~et conduit 32 adapted for connection throughsuitable valving to a source of fluid under pressure. The annular space 28, in
turn, is coMected through ports 34 in the buffer ring 14 to an inner annular space
36.
Formed in the outer periphery of the small diameter portion 20 of
piston 16 is a reduced ~diameter area portion 38. Extending through the piston 16
is an internal bore 40. In the position of the piston shown in the drawing, the
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annular space 28 is connected through ports 34, annular space 36) and the
reduced diameter area 38 to the underside 41 of the lsrge diameter portion 18 of
piston 16. Consequently) under these circumstances, lluid under pressure will
force the piston 16 upwardly until the lower edge 42 of the reduced diameter area
38 intersects the upper edge 44 of the amlular space 36. At this point, the source
of fluid under pressure, not shown, is disconnected or cut off from the underside
41 of the large diameter piston portion 18; however the piston 16 will continue its
upward movement due to the momentum imparted to it as well as the expansion
- of air trapped under the piston in chamber llA. During the initial upward stroke
of the piston 16~ air within the chamber ll is exhausted through exhaust ports 46;
However, after the lower edge 42 of area 38 intersects the upper edge 44 of
annlar space 36, a point is reached where the air within chamber 11 is no longer
exhausted-through ports 46 (i.e., after the upper side 52 of piston portion 18
intersects the upper edge 90 of exhaust port 46). The remaining air in chamber ll
then compresses to decelerate the upw~rd stroke of the piston 16. As the piston
16 countinues its upward movement, a point will be reached where the lower edge
of portion 18 reaches lower exhaust port edge 91 whereby air in chamber 11,~,
begins exhausffng out of ports 46~ The lower edge 48 of piston portion 20
intersects the lower edge 50 of the annular space 36 sometime later. Under
these circumstances, the inlet port 30 is connected through ports 34, annular
space 36 and the internal bore 40 in the piston 16 to the upper side 52 of the l~rge
diameter piston porffon 18. Consequently, ths piston is now forced downwardly
with pressure being applied to the upper side 52 until the lower edge 48 again
inersects the lower edge 50 of annular space 36. At this point, the upper side 52
of the piston is disconnected from the source of fluid under pressure; however
- the piston will continue its downward movement unt~ it strikes the tappet 22.
As the piston moves downwardly, a point is reached where fluid under pressure in
the cylinder portion 11 is exhausted throu~h the ports 46. Thus, as long as fluid
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under pressure is supplied to the annular sp~ce 28, a continuPl reciprocating or
hammering motion of the piston 16 will be achieved.
Surrounding the lower cylinder portion 12 is a cylindrical sheath 56. The
ports 46 communicate with an annular space 54 formed between the outer wall of
the cylindrical portion 10, the cylindr;cal sheath 56 and an outer wall 58
- preferably formed of an elastomer or the like. Disposed within the space 54 are
annular spacers 60 formed`of an elastomer or the like, each spacer 60 has
openings 62 therein, with the openings in one spacer being displaced 90 about
the cylinder axis with respect to those in the next ad~acent spacerO The
exhaus~ed air, after passing through the openings 62 in spacers 60 finally vents to
the atmosphere through port 64.
Disposed on the outer periphery of the wall 58 is a pair of laminated
aluminum or the like sheaths 66. These are spaced from the final outer wall 68
of the assembly, also formed from an elastomer, by an annular space 70.
Although the invention has been shown in connection with a certain
specific embodiment, it will be readily apparent to those skilled in the art that
various changes in form and arrangement of parts may be made to suit
requirements without departing from the spirit and scope of the invention. In
this respect, it will be apparent that while the the terms "upper"9 "lower"9
~O nupward" and "downward" are used herein and in the appended claims to describe
the cylinder and piston parts, the invention is not limited to a vertical
- configuration and can be used in any inclination with respect to vertical, and can
even be inverted.
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