U.S. patent number 3,850,255 [Application Number 04/847,294] was granted by the patent office on 1974-11-26 for power driven hammers or the like.
This patent grant is currently assigned to Rockwell International Corporation. Invention is credited to Heinrich P. Koehler.
United States Patent |
3,850,255 |
Koehler |
November 26, 1974 |
POWER DRIVEN HAMMERS OR THE LIKE
Abstract
Power driven hammers or the like in which a closed type,
cushioned tool holder is axially impacted by a free-floating driver
mounted in a reciprocably driven, non-rotatable piston and also
intermittently rotated and in which the mechanism producing
intermittent rotation is of the ratchet type and has input and
output members which are biased into driving engagement but
disengage when a rotation restraining force of a predetermined
magnitude is exerted on the tool holder. The input member is
drive-connected to and rotated back-and-forth by the piston as the
piston reciprocates.
Inventors: |
Koehler; Heinrich P. (Camillus,
NY) |
Assignee: |
Rockwell International
Corporation (Pittsburgh, PA)
|
Family
ID: |
25300284 |
Appl.
No.: |
04/847,294 |
Filed: |
August 4, 1969 |
Current U.S.
Class: |
173/110;
173/210 |
Current CPC
Class: |
B25D
16/003 (20130101) |
Current International
Class: |
B25D
16/00 (20060101); E21c 003/04 (); B25d 009/04 ();
B25d 009/06 () |
Field of
Search: |
;173/47,110,111,139 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Leppink; James A.
Claims
What is claimed and desired to be secured by Letters Patent is:
1. A power driven device, comprising: a casing; a tool holder;
means mounting said tool holder for rotation in said casing; a
cyclically operable impact imparting mechanism for imparting axial
impacts to said tool holder; means for reciprocating said impact
imparting mechanism in said casing; and means so drive-connecting
said impact imparting mechanism to said tool holder that, in each
cycle of operation of said impact imparting mechanism, said
mechanism rotatably advances said tool holder, said drive
connecting means comprising rotatably mounted, axially aligned
input and output means; first means so drive-connecting said impact
imparting mechanism to said input means that said input means is
rotatively oscillated as said impact imparting mechanism
reciprocates; second means for so drive-connecting said input means
to said output means that said output means is rotatively advanced
by said input means as said input means moves in one of its
directions of movement only; and third means connecting said tool
holder to said output means for rotation therewith, all of the
first means connecting the impact imparting mechanism to said input
means and said input means being rectilinearly movable in said
casing along the axis along which said input and output means are
aligned.
2. The device of claim 1, wherein said impact imparting mechanism
includes a rectilinearly reciprocable piston, said input means
includes a rotatable drive member having a bore therein into which
said piston extends, said input means being integral with said
drive member, and said first means comprises external helical
splines on said piston and internal helical splines in the bore of
said drive member.
3. The device of claim 1, wherein the third means connecting said
tool holder to said output means comprises external splines on one
of these components and co-operating internal splines on the other
of said components.
4. The device of claim 1, wherein said casing has an internal
annular shoulder therein for retaining said tool holder in said
casing, the device also including an annular shock absorbing member
in said casing between said shoulder and the end of the tool holder
facing said shoulder.
5. The device of claim 1, wherein said second drive-connecting
means comprises co-operating drive elements on said input and
output means and including means biasing said elements into driving
engagement, said co-operating elements being configured to allow
the elements on the input means to ride out of engagement with the
elements on the output means despite the force exerted by said
biasing means while a rotation restraining force of a predetermined
magnitude is exerted on said output means.
6. The device of claim 1, together with means mounting said tool
holder for rectilinear movement in the nose portion of said casing,
said casing having means for retaining the tool holder therein and
an opening in the nose end thereof through which a tool can be
inserted for connection to said tool holder, said tool holder
having a blind tool receiving bore therein with the closed end of
the bore being the furthermost from the nose end of the casing, and
there being a sealing member extending completely around and
engaging the periphery of the tool holder and the inside of the
casing, whereby foreign matter is prevented from penetrating beyond
the work holder into the interior of the casing.
7. A power driven device according to claim 6, wherein the opening
in the nose end of the casing has a non-circular configuration,
whereby said casing will restrain against rotation a tool inserted
therethrough which has a matching external configuration.
8. The device of claim 6, wherein the tool receiving bore in the
tool holder has a non-circular configuration, whereby a tool
inserted into said bore and having a matching external
configuration is connected to said tool holder for rotation
therewith.
9. A power driven device, comprising: a tool holder; a
rectilinearly reciprocable impact imparting mechanism having a
working stroke in which it axially impacts said tool holder and a
return stroke, a rotatable driven member, said tool holder being
fixed to said driven member for rotation therewith; a rotatable,
unitary, axially movable driving member disposed between said
driven member and said impact imparting mechanism, there being
co-operating means on said impact imparting mechanism and said
driving member for converting the rectilinear movement of said
impact imparting mechanism during its working and return strokes
into alternately oppositely directed rotary movements of said
driving member and means on said driving member engageable with
co-operating means on said driven member to rotatably advance said
driven member and therefore said tool holder as said driving member
is rotated in one of said opposite directions, said means being
constructed to permit the driving member to rotate relative to the
driven member as it rotates in the other of said opposite
directions; and means biasing into engagement the co-operating
means on said driving and driven members.
10. The device of claim 9, wherein the rectilinearly reciprocable
impact imparting mechanism includes a cylindrical piston having one
closed end and an impact producing driver slidable in said piston
and extending through the other end of the piston, said piston
being so ported as to permit the formation of air cushions in the
opposite ends of said piston as said driver moves back and forth
therein.
11. The device of claim 10, together with drive means for
reciprocating the piston of the impact imparting mechanism
comprising a rotatably mounted crank having an eccentric crankpin
thereon; a connecting rod pivotally fixed to said crankpin; and
means pivotally fixing said connecting rod to said piston.
12. The device of claim 10, together with drive means for
reciprocating the piston of the impact imparting mechanism
comprising a rotatably mounted crank; an eccentrically mounted
crankpin; a crosshead having a slot extending at right angles to
the direction of reciprocation of said piston, said crankpin
extending through said slot; guides confining said crosshead to
rectilinear, reciprocal movement in the same direction as said
piston; and means fixing said crosshead to said piston.
13. A power driven device, comprising: a casing having a nose
portion; a tool holder rectilinearly movable in the nose portion of
said casing; a rectilinearly reciprocable impact imparting
mechanism having a working stroke in which it imparts an axial
impact to said tool holder and a return stroke and including a
piston and a driver mounted in said piston and engageable with said
tool holder; drive means for reciprocating said piston; and a
component mounted in and restrained against rotation relative to
said casing, said piston being rectilinearly movable in said
component and said component and said piston having co-operating
means for restraining said piston against rotation relative to said
component.
14. The device of claim 13, wherein said co-operating means
comprise external splines on said piston and internal splines in
the component in which said piston is rectilinearly movable.
15. A power driven device, comprising: a casing having a nose
portion; a tool holder rectilinearly movable in the nose portion of
said casing: a rectilinearly reciprocable impact imparting
mechanism in said casing for producing axial impacts on said tool
holder; a motor; and a motion transmitting and converting means
drive-connecting the motor to the impact imparting mechanism, said
last-mentioned means comprising a crank mounted with its axis of
rotation at right angles to the axis of reciprocation of the impact
imparting mechanism and means connecting said crank to said
mechanism, said motor having a rotatable output shaft and being
mounted with the axis of rotation of said shaft in parallel, spaced
relationship to the axis of rotation of said crank and between said
last-mentioned axis and the nose portion of said casing, and said
motion transmitting and converting means further comprising means
drive-connecting said motor output shaft to said crank.
16. The device of claim 15, wherein the means connecting said crank
to the impact imparting mechanism comprises an eccentrically
mounted crankpin on said crank, a connecting rod pivotally fixed to
said crank, and a wrist pin pivotally fixing said connecting rod to
said impact imparting mechanism.
17. The device of claim 15, wherein the means drive-connecting the
motor output shaft to said crank is gear teeth on said shaft and
gear teeth around the periphery of said crank intermeshing with
those on the motor output shaft.
18. A power driven device, comprising: a rectilinearly reciprocable
impact imparting mechanism; a motor; motion transmitting and
converting means drive-connecting said motor to said impact
imparting mechanism; a rotatably mounted tool holder; and means so
drive-connecting said impact imparting mechanism to said tool
holder that rectilinear movement of said mechanism produces rotary
movement of the tool holder, said last-mentioned means including a
torque responsive clutch for effectively interrupting the drive
connection between the impact imparting mechanism and the tool
holder while rotation resisting forces of at least a predetermined
magnitude are exerted on said tool holder which comprises a
rotatable, axially fixed output member connected to said tool
holder for rotation therewith, a rotatable, axially movable input
means, and cooperating first and second means on said input means
and output member, respectively, for providing a drive connection
therebetween, said co-operating means being so configured as to
permit those on the input means to override those on the output
member when said rotation restraining force of predetermined
magnitude is reached to thereby permit said input means to rotate
relative to said output member, and the means for drive-connecting
the impact imparting mechanism to the tool holder also including an
axially movable, rotary drive means which is integral with said
rotatable input means and rotatable by said impact imparting
mechanism as the latter reciprocates and means biasing said rotary
drive means and said clutch input means toward said clutch output
member to engage the drive connection providing means on the input
means with the co-operating drive connection providing means on the
output member so that the drive connection providing means on the
input means will override the co-operating means on the output
member only upon the rotation resisting force reaching said
predetermined magnitude and overcoming the clutch engaging force
exerted by said biasing means.
19. A power driven device, comprising: a tool holder; a
rectilinearly reciprocable impact imparting mechanism having a
working stroke in which it axially impacts said tool holder and a
return stroke; a rotatable driven member, said tool holder being
fixed to said driven member for rotation therewith; a rotatable,
axially movable, unitary driving member disposed between said
driven member and said impact imparting mechanism, there being
co-operating means on said impact imparting mechanism and said
driving member for converting the rectilinear movement of said
impact imparting mechanism during its working and return strokes
into alternately oppositely directed rotary movements of said
driving member and means on said driving member engageable with
co-operating means on said driven member to rotatably advance said
driven member and therefore said tool holder as said driving member
is rotated in one of said opposite directions, said means being
constructed to permit the driving member to rotate relative to the
driven member as it rotates in the other of said opposite
directions; means biasing into engagement the co-operating means on
said driving and driven members; and means fixing said driven
member against axial movement, there being an annular flange on
said driving member and said biasing means comprising a compression
spring surrounding said driving member, one end of said spring
bearing against said flange and the other end of said spring being
axially fixed.
20. A power driven device, comprising: a casing having a nose
portion; a tool holder; means mounting said tool holder for
rectilinear and rotary movement in the nose portion of said casing;
a rectilinearly reciprocable impact imparting mechanism having a
working stroke in which an axial impact is produced on said tool
holder and a return stroke and including a cylindrical piston
having one closed end and a driver slidable in said piston and
extending through the other end of the piston, said driver being
engageable with said tool holder and said piston being so ported as
to permit the formation of air cushions in the opposite ends of
said piston as said driver moves back and forth therein; drive
means for reciprocating said piston which comprises a wobble plate,
means mounting said wobble plate for pivotal movement about a pivot
axis extending at right angles to the direction of movement of the
piston of the impact imparting mechanism, means pivotally fixing
said wobble plate to said piston, a cam engageable with said wobble
plate for pivoting said plate about its pivot axis, and means
mounting said cam for rotation about an axis disposed at right
angles to said pivot axis; and means having rotatably mounted input
element and output elements drive-connected between said piston and
said tool holder for converting the rectilinear movement of said
piston into intermittent rotary motion of said tool holder and for
permitting said input member to slip relative to said output member
while rotation restraining forces of at least a predetermined
magnitude are exerted on said tool holder.
21. A power driven device, comprising: an impact imparting
mechanism, means mounting said impact imparting mechanism for
reciprocable rectilinear movement; a motor; motion transmitting and
converting means drive-connecting said motor to said impact
imparting mechanism for cycling said mechanism through oppositely
directed working and return strokes; a rotatably mounted tool
holder; and means so drive-connecting said impact imparting
mechanism to said tool holder that, during one of the strokes in
each cycle thereof, said mechanism rotatably advances said tool
holder, said mechanism not effecting rotation of the tool holder in
the other stroke of each cycle thereof, the means drive-connecting
the impact imparting mechanism to the tool holder comprising
ratchet means including axially aligned, rotatable input and output
members, means connecting said output member to said tool holder
for rotation therewith, and means rotating said input member back
and forth as said impact imparting mechanism moves in opposite
directions, there being co-operating first and second means on said
input and output members, respectively, which are engageable when
said input member is rotated in one direction only to rotatably
advance said output member and said tool holder and the means for
rotating the input member back and forth including one means
incorporated in the rotatable input member and a co-operating means
incorporated in the impact imparting mechanism, said rotatable
input member, said co-operating first means on said input member
and said one means incorporated in the rotatable input member
comprising a one piece, integral member.
Description
This invention relates to power driven devices and, more
particularly, to power driven devices for drilling holes in or
otherwise working concrete, masonry, and the like by axially
impacting a tool against the workpiece, either with or without
intermittent rotation of the tool depending upon the task and the
material involved.
One primary object of the present invention resides in the
provision of novel, improved power driven devices of the type just
described.
A number of tools for drilling holes in or otherwise working
concrete, masonry, rock, and similar materials have heretofore been
proposed, including those described in U.S. Pat. Nos. 1,191,148;
1,601,644; 2,283,292; 2,533,481; 2,558,165; 3,256,944; 3,334,693;
3,456,740; and 3,456,743; in German Patents 121,394 153,320; and
306,148 and in Robert Bosch GmBH Spare Parts List No. EW-EWV
2/302/IX (11.64) and Metabo Elektrowerkzeuge Spare Parts List For
Bohrhammer 1130 dated February 1969. However, in each instance, the
previously proposed devices have drawbacks which it would be
desirable to eliminate. Among these are undue complexity,
unwieldiness, excessive size and/or weight, poor balance,
inadequate protection against the penetration of foreign matter to
the interior of the device, and similar factors. In addition many
such tools heretofore proposed operate less than satisfactorily
and/or make no provision for protecting the operator from injury or
the device against damage if the tool sticks.
In the novel power driven hammers of the present invention by which
the foregoing and other deficiencies of the heretofore available
devices are remedied, the motor of the device, which is preferably
disposed at right angles to the longitudinal axis of the hammer, is
connected through a rotary-to-reciprocating motion converting
mechanism to an impact producing mechanism consisting of a
reciprocable piston in which a free-floating driver is slidably
mounted. The driver is dimensioned to strike a closed type tool
holder to impart axial impacts to a tool in the holder. Controlled
flow of air into and out of the piston on opposite side of the
driver produces positive forces for propelling the driver through
its working and return strokes and provides cushions which prevent
the driver from striking the ends of the piston as it moves
back-and-forth therein.
During each cycle of the impact imparting mechanism the tool socket
is rotatably advanced through an angle of preselected magnitude by
a novel motion transmitting mechanism driven by the piston. This
mechanism is also torque responsive and interrupts the rotary drive
connection between the piston and tool socket if the tool binds or
sticks.
Depending upon the operation involved, the intermittent rotary
motion of the tool socket may or may not be transmitted to the tool
itself. This provides a choice between axial hammering alone or
axial hammering plus intermittent rotation of the tool.
The novel power hammer just described is compact and relatively
light and has good balance due to the manner in which the motor is
positioned with respect to the rotary-to-reciprocatory motion
converting mechanism. It is also rugged, providing a long service
life, and uncomplicated, making it comparatively inexpensive to
manufacture and maintain.
Furthermore, the novel power hammers of the present invention are
highly effective in drilling and like operations because of the
intermittent rotation imparted to the tool in conjunction with
axial impacts. And, as will be discussed in more detail later, the
specific impacting mechanism and intermittent rotary motion
producing mechanism of the present invention contribute to positive
operation and improved performance.
Also, the torque responsive overload release feature incorporated
in the intermittent rotary motion producing mechanism is of
considerable importance. This feature prevents a binding or
sticking tool from causing damage to the hammer or injury to its
operator as it keeps the motor from driving the hammer about a
stuck tool.
Further, the novel closed type tool holder employed in the hammers
of the present invention has been found highly effective in
preventing foreign matter from penetrating to the interior of the
hammer casing. This also contributes to proper operation of the
hammer and to long service life.
One primary object of the present invention has been identified
above. Another important and primary object of the invention
resides in the provision of novel, improved power driven hammers
which do not have the above-discussed disadvantages of previously
available devices of this type.
Other important but more specific objects of the present invention
reside in the provision of novel, improved power driven hammers,
which:
1. are compact and relatively light and well balanced.
2. are rugged and uncomplicated and therefore have a long service
life and are relatively inexpensive to manufacture and service.
3. are versatile.
4. are particularly effective for drilling holes in concrete,
masonry, rock, and the like.
5. include a mechanism for producing both axial impacts on and
intermittent rotation of a tool or bit.
6. have a torque responsive overload release mechanism for
preventing damage to the hammer and/or injury to the operator in
case of a struck bit or the like.
7. are constructed to minimize the penetration of foreign matter to
the interior of the hammer.
8. have various combinations of the desirable attributes just
discussed.
Other objects and features and additional advantages of the
invention will become apparent from the appended claims and as the
ensuing detailed description and discussion proceeds in conjunction
with the accompanying drawing, in which:
FIG. 1 is a side view of a power driven hammer constructed in
accord with the principles of the present invention, part of the
hammer casing being broken away to show certain of its internal
components;
FIG. 2 is a portion of the hammer of FIG. 1 to an enlarged scale
with the casing and part of the internal components in section;
FIG. 3 is a section through the hammer of FIG. 1 taken
substantially along line 3--3 of FIG. 1, showing the driver and
reciprocating piston of an axial impact producing mechanism
employed in the hammer and the member in the piston is mounted;
FIG. 4 is a section taken substantially along line 4--4 of FIG. 2,
showing the piston of the impact imparting mechanism and the input
member of an intermittent rotary motion producing and torque
responsive overload release mechanism which is driven by the piston
as the latter reciprocates in the hammer casing;
FIG. 5 is a fragmentary side view of the piston and the input
member of the intermittent rotary motion producing mechanism with
the latter sectioned to show the manner in which it is
drive-connected to the piston;
FIG. 6 is a section through the hammer taken substantially along
line 6--6 of FIG. 2, showing the output member of the rotary motion
producing mechanism, a tool socket which is driven by the output
member, and the forward end of hammer casing;
FIG. 7 is a side view of the input and output members of the
intermittent rotary motion producing mechanism illustrating the
drive connection therebetween;
FIG. 8 is a view similar to FIG. 2 of an alternate form of
intermittent rotary motion producing mechanism which may be
employed in the hammers of the present invention.
FIG. 9 is a view similar to FIG. 1 of another embodiment of the
invention;
FIG. 10 is a transverse section through a Scotch yoke mechanism
employed in the hammer of FIG. 9;
FIG. 11 is a view similar to FIG. 1 of yet another form of the
invention.
FIG. 12 is a side view of one form of tool which may be used in the
hammers of the present invention; and
FIG. 13 is a fragmentary side view of a second type of tool which
may be employed in the hammers of the present invention when axial
hammering without rotary motion of the tool is desired.
Referring now to the drawing, FIG. 1 depicts a power driven hammer
18 constructed in accord with the principles of the present
invention. The major components of hammer 18 include a casing 20
housing a motor 22 drive-connected through rotary-to-reciprocable
motion converting mechanism 24 to the piston 26 of an impact
imparting mechanism 28 which also includes a free-floating driver
30 slidably mounted in the piston. Driver 30 is adapted to
periodically strike and impart axial impacts to an axially movable
tool holder 32 mounted in the forward end of casing 20 and thence
to a tool 34 (see FIG. 2) in holder 32. Tool 34 may also be
intermittently rotated or advanced during each working stroke of
piston 26 by the piston, which is drive-connected to tool holder 32
through a ratchet type drive arrangement 36. Drive mechanism 36 is
also designed to serve an overload function, i.e., to interrupt the
drive connection between piston 26 and tool holder 32 if the
rotation resisting torque exerted by the tool 34 rises above a
predetermined magnitude.
Tool 18 also includes a pistol grip 38 supporting a switch 40 for
controlling the operation of motor 22. The details of these
components are not part of the present invention and will
accordingly not be described further herein.
Considering now the novel tool 18 just described in more detail,
motor 22 is supported in depending casing section 42 in a
conventional manner at a right angle to the longitudinal axis of
hammer 18, an arrangement which is preferred as it eliminates the
need for comparatively expensive bevel gears in drive train 24.
Also, as shown in FIG. 1, the motor shaft 44 is located forwardly
of a crankshaft 45 incorporated in drive train 24. This shortens
the hammer, making it more compact. Also, it places the center of
gravity of the hammer closer to its grip 38, thereby improving the
balance of the hammer and making it easier to handle. The output
shaft 44 of the motor extends vertically through a bearing 46 in
the upper end of casing section 42 into the interior of a casing
section 48 where a pinion 50 fixed to or integral with its upper
end meshes with a gear 52 fixed to the crankshaft 45 just
mentioned.
Referring still to FIG. 1, crankshaft 45 is rotatably supported in
casing section 48 in bearings 56 and 58. Lower bearing 56 is seated
in a recess 60 formed in a boss 62 which protrudes from the rear
wall 64 of casing section 48. Upper bearing 58 is supported from
the top wall 66 of lower casing section 42 by a conventional
bearing holder 68 of the configuration illustrated in FIG. 1.
Rotary motion of crankshaft 45 produced through the arrangement
just described in translated into longitudinal, rectilinear
movement of piston 26 by crankpin 70, connecting rod 72, and wrist
pin 74. Crankpin 70 is fixed to or made integral with crankshaft 45
and is located at the periphery thereof in conventional fashion.
One end of connecting rod 72 is fixed to the crankpin with a
bearing 76 being disposed between the crankpin and connecting rod
to permit the elements to rotate freely with respect to each
other.
The opposite end of connecting rod 72 is pivotally fixed to the
rear wall member 78 of piston 26 by wrist pin 74, which extends
through apertures 80 and 82 in member 78 and an aperture 84 through
a boss 86 on the forward end of the connecting rod.
Referring now to FIGS. 1-3, piston 26 is supported for rectilinear
movement in casing section 48 by a piston guide 88 and by the input
or drive member 90 of the ratchet type motion transmitting
mechanism 36. Piston guide 88 has a cylindrical main portion 92 and
a radial flange 94 and is fixed in casing section 48 by fasteners
96 which extend through flange 94 and are threaded into the casing
section. Cooperating external splines 98 on piston wall member 78
and internal splines 100 in the cylindrical portion 92 of piston
guide 88 keep piston 26 from rotating or twisting in the guide as
it is reciprocated by motor 22 acting through motion converting
mechanism 24.
As best shown in FIG. 2, the free floating driver 30 referred to
above, which is the other component of the axial impact producing
mechanism, has a head 102 dimensioned for a sliding fit in the main
body portion 104 of piston 26 and a smaller diameter stem 106
dimensioned for a sliding fit in the necked down forward portion
108 of the piston. Driver 30 is propelled into engagement with tool
holder 32 as piston 26 moves forwardly in casing 20 and displaced
toward the rearward end of the piston during the return stroke of
the latter by the controlled ingress of air into piston 26 on
opposite sides of driver head 102 and the controlled egress of air
therefrom through ports 110 in the piston.
More specifically, with reference to FIGS. 1 and 2, piston 26 is
shown in its forwardmost position with driver 30 moving forwardly
in the piston to impart an axial blow to tool holder 32 and thereby
drive tool 34 in the direction indicated by arrow 111 in FIG. 2. At
this point ports 110 in piston 26 are partly uncovered.
Accordingly, there is no pressure differential between the exterior
of the piston and the chamber 112 between driver head 102 and
piston rear wall member 78.
Upon rebound and approximately as piston 26 changes direction and
moves rearwardly, driver 30 rebounds toward the rear of the hammer
drill. This movement is initially relatively unimpeded because of
the comparatively low pressure in chamber 112 and the force exerted
by air trapped in the chamber 113 between the forward end of driver
head portion 102 and the reduced diameter portion 108 of piston 26.
As the piston and driver continue to travel rearwardly, the forward
portions of ports 110 are uncovered. This permits compressed air to
escape from chamber 113 and seals chamber 112 in which the pressure
therefore begins to increase.
Next, the piston reaches its rearwardmost position, reverses
direction while driver 30 is still travelling toward the rear end
of hammer 18 and moves forwardly, further increasing the pressure
in chamber 112 until the air is sufficiently compressed to overcome
the inertia of the still rearwardly moving driver. This compressed
air expands, propelling driver 30 forwardly into impacting
engagement with tool holder 32. The air compressed in chamber 112
also provides a cushion which keeps the driver from striking and
possibly damaging the piston during its rearward movement in the
portion of the impact mechanism operating cycle just described.
As the driver is driven forward, toward tool holder 32, by the
expansion of air in chamber 112, the forward ends of ports 110 are
closed, sealing chamber 113 from the ambient atmosphere. Thus the
pressure in chamber 113 increases as the driver approaches the
forward end of the piston. This provides a cushion which keeps the
driver from striking the forward part of the piston, even if there
is no tool in the holder or the hammer is idling with the tool
holder forward in casing member 114 and out of contact with driver
30.
The double-acting air cushion arrangement just discussed can, of
course, be replaced by other types of impact mechanisms, if
desired. The doubling-acting type is preferred, however, because
positive pressures are available to effect both the forward and
rearward motion of the driver in contrast to other types in which a
negative pressure or vacuum is at least in part utilized to effect
movement of the driver or striker. Also, the air cushions produced
in the preferred arrangement are highly effective in preventing the
driver from striking and damaging the piston. This is a significant
factor in long service life.
Turning now to FIGS. 1, 2 and 6, the tool holder 32 against which
driver 30 impacts includes a cylindrical main body portion 115 in
which a tool receiving socket 116 is formed and a closed rear wall
117, which prevents foreign matter from penetrating through the
tool socket to the interior of casing section 48.
Tool holder 32 is mounted for rectilinear movement in the forward
section 114 of tool casing 20 with a flange 118 at its nose 120
slidingly engaging the interior of casing section 114. An O-ring
122 disposed in a recess 124 formed in tool holder nose portion 120
prevents foreign matter from penetrating to the interior of the
tool casing around the tool holder.
A ring 126 of resilient material is preferably disposed in the
forward end of casing section 114 in spaced relation to tool holder
32. This ring keeps tool holder 32 from striking and damaging the
casing with motor 22 running and hammer 18 idling or with no tool
in the tool holder.
Referring now to FIGS. 1, 2 and 6, the main body portion 115 of the
tool holder extends into a bore 128 through the output or driven
member 130 of ratchet type rotary motion transmitting mechanism 36.
Member 130 is rotatably mounted in casing section 114, but is fixed
against axial movement by an annular ledge 131 in casing section
114 and a similar ledge 132 at the forward end of intermediate
casing section 133, which engage opposite sides of a flange 134 on
member 130. External splines 135 on the main body portion 115 of
the tool holder and cooperating internal splines 136 in the bore
128 of driven member 130 connect the tool holder to output member
130 for rotation therewith.
Turning next to FIGS. 1, 2, 4 and 6, the drive or input member 90
of intermittent rotary motion producing mechanism 36 mentioned
briefly above includes a main body section 137 provided with an
internal bore 138 through which the forward end portion 108 of
piston 26 extends. Input member 90 is rotatable and axially movable
in a bore 139 through an annular boss 140 in intermediate casing
section 133.
As shown in FIG. 5, helical external splines 141 are formed on the
forward end portion 108 of piston 26, and cooperating, internal,
helical splines 142 are formed in the bore 138 of drive member 90.
Accordingly, as piston 26 is reciprocated by the mechanism
described above, it effects an oscillatory or to-and-fro rocking
movement of drive mechanism input member 90 through an angle
determined by the configuration of cooperating splines 141 and
142.
Referring now to FIGS. 1, 2 and 7, the forward end of input member
90 terminates in an annular flange 144, which faces the annular
flange 134 at the rear end of driven member 130. Ratchet teeth 146
are formed on the face 148 of drive member 90 provided by flange
144, and cooperating ratchet teeth 150 are formed on the face 151
provided by the flange 134 at the rear end of output member
130.
As shown in FIG. 7, the teeth 146 on input member 90 have a steep
leading edge 152 and a trailing edge 154 with a relatively gentle
slope. The teeth on output member 130 are similarly configured but
face in the opposite direction.
Accordingly, with teeth 146 and 150 in engagement as shown in FIG.
7, input member 90 drives output member 130 when it is oscillated
by piston 26 in the direction shown by arrow 156. However, when it
is oscillated in the opposite direction as shown by arrow 158 in
FIG. 7, teeth 146 slide over the teeth 150 on output member 130;
and no rotary motion is imparted to the output member.
Referring now to FIGS. 1 and 2, input member 90 and output member
130 are normally maintained in the driving relationship shown in
FIG. 7 by a compression spring 160, which abuts an annular ledge
162 on input member 90 at its forward end. The rear end of this
spring engages an annular ledge 164 formed at the rear end of the
intermediate casing section 133 in which the input member is
disposed.
Thus, depending upon the inclination of the cooperating helical
splines 141 and 142 on the piston and input member, respectively,
the piston is effective upon its forward or return stroke to rotate
input member 90 in a direction in which it will rotatably advance
output member 130. This rotary advance is transmitted to tool
holder 32 by the cooperating external splines 135 on the tool
holder and 136 in the bore through the output member. This
incremental advance is in turn transmitted to tool 34 because of
the matching configurations of the tool socket 116 and the shank
166 of the tool. Typically, this configuration will be hexagonal
although any configuration which will drive connect the tool to the
tool socket may be employed.
The novel intermittent rotation just described has proven to
contribute significantly to the operation of the present invention,
especially in drilling operations in which spiral fluted bits 34 of
the type illustrated in FIG. 12 are employed. This particular
mechanism produces high acceleration rates, making the illustrated
type of bit highly effective in breaking off chips in the borehole
and also facilitates the movement of the chips up the bit and out
of the borehole.
As indicated above, the driving and driven members 90 and 130 of
rotary motion transmitting mechanism 36 constitute a torque
responsive overload release as well as a mechanism for
intermittently rotatably advancing tool 34. More specifically, as
discussed above, compression spring 160 normally maintains the
input and output members in driving engagement as shown in FIG. 7.
However, if tool 34 becomes stuck or a rotation restraining torque
is otherwise exerted upon it, this restraint will be transmitted
through tool holder 32 to output member 130 through the drive
connections discussed above.
With the output member thus restrained against rotation, input
member 90 will still be rotatably oscillated by piston 26 as it
reciprocates in casing 20. However, as the input member rotates in
the direction indicated by arrow 156 in FIG. 7, its teeth 146 will
simply ride up the leading edges of the teeth 150 on output member
130 despite their rather steep inclination. This forces input
member 90 away from output member 130 against the bias exerted by
spring 160 and allows it to slip relative to the driven member.
Such slippage continues until the rotation restraining force is
removed from output member 130. This is an important safety feature
as it keeps motor 22 from driving hammer 18 around a stuck tool and
hitting the operator or damaging the hammer and also prevents the
motor from stalling and suffering damage if a toool sticks.
Another unique advantage of the novel mechanism 36 just described
is that a stuck bit may be freed by shutting off the power to motor
22 and then rotating hammer 18 about the tool in the drilling
direction to impart a rotary impact to and thereby free the tool.
In heretofore available hammers such procedure turns the hammer
motor, and no impact is exerted on the stuck bit.
As will be discussed hereinafter, the arrangement of the components
in mechanism 36 can be varied, if desired. The arrangement just
described is preferred, however, as it has proven the most
effective in keeping the input and output members 90 and 130 of
mechanism 36 in firm driving engagement, even under the vibration
produced by the rebounding driver and tool holder. Moreover,
eccentricities in and cocking of tool 34 are accommodated in the
axially fixed output member 130. This has proven more satisfactory
than in alternate arrangements in which the output member is
axially movable.
Also, in conjunction with the foregoing, it was indicated above
that the intermittent rotary advance of the tool can be effected on
either the working or the return stroke of piston 26. It is
preferred, however, that this motion be effected during the forward
stroke. In this case friction between the helical splines on the
piston and those in driving member 90 biases the teeth on the
driving member into and keeps them in engagement with the teeth on
the drive member while the driving part of the ratcheting motion
occurs. Also, the frictional force between the helical splines
tends to keep the driving and driven members from separating due to
rebound under impact. Moreover, on the return stroke the frictional
force acts in the opposite direction to retract the driving member
and facilitate the ratcheting of member 90 relative to output
member 130.
The foregoing description of an exemplary embodiment of the
invention was concerned with applications of the invention in which
it is desired to impart both axial impact and intermittent rotary
movement to the tool 34. However, this exemplary impact hammer may
equally well be employed for applications where axial impact
without rotary movement is desired. For such applications, tools
with the shank configuration discussed above are replaced with a
tool of the type identified by reference character 168 in FIG. 13
in which the rearward portion 170 of the tool shank is cylindrical
and the forward portion 172 has a hexagonal or other non-circular
configuration configured for sliding fit in a socket 174 formed in
the forward end of casing member 114.
The connection between shank portion 172 and socket 174 keeps tool
168 from rotating in the housing member. And, as the rear shank
portion 170 extending into the socket 116 in tool holder 32 is
circular, there is no driving connection between the tool socket
and the tool. Thus, while motion transmitting mechanism 36
continues to rotatably advance tool socket 32 in the manner
previously discussed, this rotary motion is not imparted to the
tool. Axial blows are however imparted to the shank of the tool by
driver 30 through the tool holder in the manner described
above.
As mentioned previously, hammers constructed in accord with the
principles of the present invention may take forms other than that
discussed above and illustrated in FIGS. 1-6. For example, FIG. 8
illustrates a hammer 176 which is similar to that just discussed
except that the input member 177 of intermittent rotary motion
producing mechanism 178 is fixed against axial rearward movement in
casing section 180 by thrust bearing 182, and the output or driven
member 183 of mechanism 178 is axially movable and is biased into
engagement with the driving member by a compression spring 184.
This spring extends between annular flange 186 at the rear of the
output member and an annular flange 188 on a support member 190
fixed between casing sections 180 and 192. While this arrangement
is satisfactory for many applications of the invention, it may
prove inferior to the alternate arrangement employed in tool 18 as
far as maintaining the inpput and output members of the
intermittent motion producing arrangement in driving engagement is
concerned.
Another modification of the present invention, incorporated in the
hammer 194 illustrated in FIGS. 9 and 10, involves the substitution
of a Scotch yoke for the crank and connecting rod employed in
hammer drill 18 to convert the rotary motion of the hammer motor to
reciprocatory motion of the piston of the impact imparting
mechanism. For the most part the components of hammer 194 may be
like those of hammer 18. Such like components have been identified
by the same reference characters as in FIGS. 1-6.
As shown in FIGS. 9 and 10, the Scotch yoke motion converting
mechanism 196 of hammer 194 includes a transversely extending
crosshead 198 integrally formed on the rear wall member 200 of
piston 26. Crosshead 198 is provided with a downwardly opening
recess 202 into which the eccentric crankpin 203 on crankshaft 204
extends.
Crosshead 198 and piston 26 are mounted for but confined to axial
longitudinal movement in casing member 206 by guides 208 and 210
which extend longitudinally in casing member 206 on opposite sides
thereof and a pin 212, which extends through crosshead 198 into
recesses 214 and 216 in guides 208 and 210, respectively.
Accordingly, as crankshaft 204 rotates, crankpin 203 moves
laterally in the recess 202 of crosshead 198, causing piston 26 to
reciprocate longitudinally in casing section 206 in the same manner
as in hammer 18 to produce axial impact and intermittent rotary
motion.
The Scotch yoke modification just discussed may prove advantageous
in many applications of the present invention. It results in a
reduction of the overall length of the hammer drill, has a small
number of components, is of light weight, and is not expensive to
build.
FIG. 11 depicts yet another hammer 218 constructed in accord with
the principles of the present invention. In this hammer the
mechanism 220 provided to convert the rotary motion of motor output
shaft 222 into reciprocable motion of piston 26 is of the wobble
plate type. Also, in this embodiment of the invention motor 224 is
mounted in a lower section 226 of hammer casing 228 with its output
shaft 222 extending rearwardly parallel to the longitudinal axis of
the hammer through casing partition 230 and a bearing 232 disposed
in aperture 234 in the partition. Integral with or attached to the
rear end of output shaft 222 is a pinion 236, which meshes with a
gear 238 fixed on a shaft 240. Shaft 240 is supported from
partition 230 in a bearing 242 fitted into an aperture 244 in the
partition.
Fixed to the rear end of shaft 240 is a member 246 carrying a
wedge-shaped wobble plate 248. The wobble plate is adapted to
engage the forward face 250 of a connecting member 252 mounted for
pivotable movement in upper casing section 253 by a laterally
extending pin 254 secured at its ends to opposite sides of casing
section 253. The head 256 of pin 254 is disposed in a slot 258
which is formed in a boss 260 integral with the rear wall member
262 of piston 26.
As shaft 240 is rotated by motor 224, wobble plate 248 rocks
connecting member 252 back-and-forth about the axis of pin 254.
This imparts the same reciprocatory motion to piston 26 as the
other forms of motion converting mechanism described above. Hammer
218 accordingly operates in the same manner as the previously
described embodiments to produce axial imparts on and intermittent
rotation of tool holder 32.
It will be apparent to those skilled in the relevant arts that
power driven hammers employing the principles of the present
invention may assume forms other than those illustrated and
described above. To the extent that they are not expressly excluded
from the appended claims, such forms of the invention are fully
intended to be covered therein.
The invention may be embodied in other specific forms without
departing from the spirit or essential characteristics thereof. The
present embodiments are therefore to be considered in all respects
as illustrative and not restrictive, the scope of the invention
being indicated by the appended claims rather than by the foregoing
description, and all changes which come within the meaning and
range of equivalency of the claims are therefore intended to be
embraced therein.
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