Portable machine tool

A machine tool comprises a mounting member for attachment to a workpiece. The mounting member includes a bearing portion that has an external surface of circular cross section and is formed with an aperture in its external surface. A utility device has an internal peripheral surface that defines a cylindrical cavity for receiving the bearing portion of the mounting member in a manner that allows the utility device to move axially and rotationally relative to the mounting member. A clamp is actuable when the utility device is fitted to the bearing portion of the mounting member for releasably retaining the utility device against axial and rotational movement relative to the bearing portion. A spring-loaded detent member projects into the cylindrical cavity from the peripheral surface and is receivable in the aperture of the bearing portion for retaining the operating assembly against axial and rotational movement relative to the bearing portion in the event that the clamp is not actuated.

BACKGROUND OF THE INVENTION 
This invention relates to a portable machine tool. 
The Model BB1149 Portable Boring Bar sold by Climax Portable Machine Tools, 
Inc. of Newberg, Oregon is a portable boring machine that is used for 
boring out a hole in a workpiece to a desired diameter and with its axis 
at a desired orientation. Referring to FIG. 1 of the drawings, spacer 
plates 4A and 4B are tack welded to opposite sides of the workpiece (not 
shown) and mounting brackets 8A and 8B are attached to the spacer plates 
respectively using screws. Each mounting bracket includes a ring portion 
that defines a circular aperture. The manner in which the mounting 
brackets are attached to the spacer plates allows movement of the mounting 
brackets relative to the spacer plates, and the mounting brackets are 
initially positioned so that the centers of the two circular apertures lie 
at least approximately on the desired central axis of the final bore. A 
mounting bearing 12 is attached to each mounting bracket in a manner 
allowing limited movement of the mounting bearing relative to the mounting 
bracket. The assembly of the mounting bearing and mounting bracket may be 
as shown in U.S. Pat. No. 4,990,037, the disclosure of which is hereby 
incorporated by reference herein. As shown in U.S. Pat. No. 4,990,037, the 
mounting bearing is generally cylindrical, having a central axis, and 
defines a passage through which an elongate boring bar extends with 
clearance. A collar defines a bore through which the boring bar extends 
with a snug fit allowing rotational and axial relative movement, and a 
spherical bearing is effective between the collar and the mounting bearing 
and allows the collar to pivot relative to the mounting bearing about a 
point that lies on the central axis of the mounting bearing. The mounting 
bearing has a spherical external bearing surface, and the center of 
curvature of the spherical bearing surface coincides with the center of 
pivotal movement of the collar relative to the mounting bearing. 
Referring again to FIG. 1, the boring bar, which is designated 16 in FIG. 
1, is fitted through the mounting bearings 12, and the positions of the 
mounting bearings are adjusted relative to the mounting brackets so that 
the central axis of the boring bar lies on the desired central axis of the 
final bore. A rotational drive assembly 22 is fitted on the boring bar. 
The rotational drive assembly includes a clamp ring 24 that defines a 
cylindrical mounting cavity. When the rotational drive assembly is fitted 
on the boring bar, the mounting bearing 12A is received in the cylindrical 
mounting cavity of the clamp ring 24, and the clamp ring 24 is then 
tightened. In this manner, the rotational drive assembly 22 is secured to 
the workpiece. The spherical configuration of the external bearing surface 
of the mounting bearing 12A allows the clamp ring to be tightened firmly 
against the bearing surface even if the central axis of the boring bar 
does not coincide with the central axis of the mounting bearing. The 
rotational drive assembly includes a motor 28 that is coupled through 
gearing (not shown) to a drive collet 32 that is fitted on the boring bar 
and is keyed thereto. Thus, when power is supplied to the motor, the 
boring bar is driven to rotate relative to the rotational drive assembly. 
An axial feed assembly 40 is also fitted on the boring bar 16. The axial 
feed assembly includes a housing 44 that is coupled to the rotational 
drive assembly through a lead screw 48 that is parallel to the boring bar 
and holds the housing 44 against rotation relative to the rotational drive 
assembly. The housing 44 contains a feed collet 52 that is rotatable 
within the housing 44 but is held against axial movement relative to the 
housing. The feed collet 52 is clamped to the boring bar 16, whereby the 
housing 44 is held against axial movement relative to the boring bar and 
the feed collet is driven to rotate inside the housing 44. The feed collet 
is drivingly coupled to a lead nut that is in threaded engagement with the 
lead screw 48. As the feed collet is rotated, the lead nut rotates and the 
axial feed assembly is moved toward or away from the rotational drive 
assembly. Thus, the boring bar is moved axially relative to the workpiece. 
Proper installation of the portable boring machine is a demanding task, and 
it is sometimes necessary that the machine be installed in a confined 
space. In these circumstances, it is possible that the operator will find 
it difficult or inconvenient to tighten the clamp ring 24 that secures the 
rotational drive assembly to the mounting bearing 12A while maintaining a 
firm grip on the rotational drive assembly. 
When the Model BB1149 Portable Boring Bar is in use, there is a possibility 
that the operator will not be attentive and the axial feed of the boring 
bar will be such that the toolhead, which is mounted on the boring bar, 
passes beyond the workpiece and collides with the mounting bracket or 
other environmental structure. This may cause damage to the boring machine 
or other structures. 
SUMMARY OF THE INVENTION 
In accordance with a first aspect of the invention there is provided a 
machine tool comprising a mounting member for attachment to a workpiece, 
the mounting member including a bearing portion that has an external 
surface of circular cross section and is formed with at least one aperture 
in its external surface, and a utility device having an internal 
peripheral surface that defines a cylindrical cavity for receiving the 
bearing portion of the mounting member in a manner that allows the utility 
device to move axially and rotationally relative to the mounting member, a 
clamp means actuable when the utility device is fitted to the bearing 
portion of the mounting member for releasably retaining the utility device 
against axial and rotational movement relative to the bearing portion, and 
at least one spring-loaded detent member that projects into the 
cylindrical cavity from said peripheral surface and is receivable in the 
aperture of the bearing portion for retaining the operating assembly 
against axial and rotational movement relative to the bearing portion in 
the event that the clamp means is not actuated. 
In accordance with a second aspect of the invention there is provided a 
machine tool for boring out a hole in a workpiece, comprising a boring 
bar, at least one mounting member for attachment to the workpiece to 
support the boring bar, the mounting member being generally cylindrical 
and defining a passage for receiving the boring bar, and including a 
bearing portion that has an external surface of circular cross section and 
is formed with at least one aperture in its external surface, and a 
rotational drive assembly including a motor in driving engagement with the 
boring bar, an attachment portion having an internal peripheral surface 
that defines a cylindrical cavity for receiving the bearing portion of the 
mounting member in a manner that allows the attachment portion to move 
axially and rotationally relative to the mounting member, a clamp means 
actuable when the attachment portion is fitted to the bearing portion of 
the mounting member for releasably retaining the attachment portion 
against axial and rotational movement relative to the bearing portion, and 
at least one spring-loaded detent member that projects into the 
cylindrical cavity from said peripheral surface and is receivable in the 
aperture of the bearing portion for retaining the attachment portion 
against axial and rotational movement relative to the bearing portion in 
the event that the clamp means is not actuated. 
In accordance with a third aspect of the invention there is provided a 
portable machine tool comprising a bar having a central axis, a rotational 
drive assembly effective between the bar and a mechanical ground for 
rotating the bar about said axis, an axial feed assembly mounted on the 
bar in a manner that prevents relative axial movement, said axial feed 
assembly including a housing, a drive member that is mounted in the 
housing and is held against axial movement relative to the housing and 
rotational movement relative to the bar, an output member that is 
rotatable in the housing about an axis that is parallel to the bar and is 
held against axial movement relative to the housing, and a means for 
converting relative rotational movement of the bar and the axial feed 
assembly into rotational movement of the output member in the housing, a 
coupling member effective between the mechanical ground and the axial feed 
assembly, the coupling member being drivingly engaged by the output member 
whereby relative axial movement of the axial feed assembly and the 
rotational drive assembly is effected in response to relative rotational 
movement of the bar and the axial feed assembly, an axial feed stop at a 
selected position along the coupling member, and a means responsive to the 
axial feed stop for disconnecting the coupling between the bar and the 
output member.

In the several figures of the drawings, like reference numerals designate 
corresponding elements. 
DETAILED DESCRIPTION 
The portable boring machine shown in FIGS. 2-8 is similar to the machine 
shown in FIG. 1 except with respect to the axial feed assembly and the 
manner in which the rotational drive assembly is mounted to the mounting 
bearing 12A. 
As shown in FIGS. 3 and 4, the mounting bearing 12A is formed with four 
slots or recesses 60 in its external spherical surface. The slots 60 are 
shown in FIGS. 3-5 as being blind, but they could extend right through the 
mounting bearing if necessary or desirable. The four slots are 
equiangularly distributed about the central axis of the mounting bearing, 
which is defined by the cylindrical passage through the mounting bearing. 
Each slot is elongated and extends parallel to the central axis of the 
mounting bearing and spans a portion of the external spherical surface of 
the mounting bearing that is at the maximum radial distance from the 
central axis of the mounting bearing. The clamp ring 24 of the rotational 
drive assembly is provided with two radial passages that are angularly 
spaced at 30.degree. about the central axis of the clamp ring, and each 
passage accommodates a detent mechanism 64. The detent mechanism 64, which 
is shown in greater detail in FIG. 5, comprises a detent pin 68 having an 
inner end 70 and an outer end that projects outwardly beyond the clamp 
ring and is provided with a knob 72. A spring 76 urges the pin 68 radially 
inward, toward a position in which the inner end 70 projects into the 
cylindrical cavity that is defined by the interior surface of the clamp 
ring 24. 
When the rotational drive assembly is applied to the mounting bearing 12A, 
the wedging action of the spherical external surface of the mounting 
bearing against the inner ends of the detent pins pushes the detent pins 
radially outward against the force of the springs 76. In general, neither 
detent pin will be aligned with one of the slots 60 when the rotational 
drive assembly is first fitted to the mounting bearing. However, the range 
of angular positions of the boring bar 16 relative to the central axis of 
the mounting bearing 12A, permitted by movement of the mounting bearing 
relative to the bracket 8A, is such that when the drive assembly 22 has 
been applied to the mounting bearing, the inner end of each detent pin is 
within the axial extent of the slots. Therefore, by rotating the 
rotational drive assembly through an angle of no more than 30.degree. in 
either sense, the rotational drive assembly will be brought to a position 
in which the inner end of one of the detent pins 68 enters one of the 
slots 60. Because it is not necessary to rotate the rotational drive 
assembly through more than 30.degree., it is relatively easy, even under 
cramped conditions, to bring a pin into engagement with a slot. By 
engaging one of the pins 68 in one of the slots 60, the rotational drive 
assembly is locked against angular and axial movement relative to the 
mounting bearing, except as permitted by the small clearance of the inner 
end of the pin in the slot, and the operator can therefore tighten the 
clamp ring 24 onto the mounting bearing without needing to hold the 
rotational drive assembly in position. Engagement of the pin in the slot 
also prevents rotation of the drive assembly relative to the mounting 
bearing in the event that the drive motor is inadvertently switched on 
before the operator has tightened the clamp ring 24 onto the mounting 
bearing 12A. When it is necessary to remove the rotational drive assembly 
from the mounting bearing, the pin can easily be withdrawn from the slot 
by pulling the knob at the outer end of the pin radially away from the 
clamp ring. 
The housing 44 of the axial feed assembly shown in FIGS. 6-8 is composed of 
two identical shells 90A, 90B that are secured together by screws. The 
feed collet 52 through which the boring bar 16 extends is located in the 
housing 44 by ball bearings 94, which are held on the feed collet 52 
between a wave cam ring 96 and snap rings 98 and engage shoulder parts 
102A, 102B of the two shells 90A, 90B respectively. In this manner, the 
feed collet 52 is supported for rotation relative to the housing and held 
against axial movement relative thereto. The feed collet 52 has axial 
quill extensions 52A, 52B on which clamp collars 106A, 106B are fitted. By 
tightening the clamp collars 106, the feed collet is secured against 
movement relative to the boring bar and the housing 44 is thereby held 
against axial movement relative to the boring bar. 
The wave cam ring 96 has two cam tracks 96A, 96B each composed of eight 
lobes. The two cam tracks are separated from one another axially of the 
boring bar by a slot 110. 
Referring to FIG. 6 as well as FIG. 7, the axial feed assembly also 
comprises a feed shaft 114 that extends coaxially, with a close sliding 
fit, within drive bushings 118A and 118B. The drive bushings 118 are 
supported within the housing 44 by roller clutches 122A, 122B 
respectively, which are clamped between the two shells 90A, 90B. In this 
manner, the feed shaft 114 is supported perpendicular to the central axis 
of the boring bar 16. The bushings 118 are held against axial movement in 
the housing 90 by snap rings (not shown) engaging housing seals (not 
shown) at the outer ends of the bushings and thrust bearings 126 at the 
inner ends of the bushings. A crank handle 130 can be applied to either 
square section end of the feed shaft for manual rotation of the feed 
shaft. 
The drive bushings 118 each have dogs at their outer end, defining slots 
134 for receiving dowel pins 138 that project from the feed shaft 114. The 
feed shaft 114 is displacable longitudinally within the drive bushings 118 
among three detented positions, defined by engagement of spring-loaded 
detent balls 142 with annular grooves 146N, 146A, and 146B in the bushing 
118B. When the detent balls engage the groove 146N, as shown in FIG. 6, 
the dowel pins 138 are clear of the slots 134 and the drive bushings are 
free to rotate relative to the feed shaft 114. When the feed shaft is 
displaced in the direction of the arrow 150, so that the dowel pin 138A 
engages the slot 134A in the drive bushing 118A and therefore the bushing 
118A and the feed shaft 114 are locked against rotation relative to each 
other, the detent balls are received in the groove 146A. Similarly, when 
the feed shaft is displaced in the opposite direction, so that the dowel 
pin 138B engages the slot 134B in the drive bushing 118B and the drive 
bushing and the feed shaft are locked against rotation relative to each 
other, the detent balls are received in the groove 146B. 
A helical gear 154 is fitted on a hexagonal profile segment of the feed 
shaft and is located between two webs 156 of the housing 44. The gear 154 
therefore does not interfere with displacement of the feed shaft 114 among 
its detented positions, and remains coupled to the feed shaft with respect 
to rotation thereof. Thrust bearings (not shown) are provided between the 
helical gear 154 and the webs 156. 
The lead screw 48 extends through the housing 44 parallel to the boring bar 
16, and an internally threaded lead screw nut 158, which is in threaded 
engagement with the lead screw 48, is fitted in the housing by bearings 
that allow the lead screw nut to rotate within the housing while holding 
it against axial movement. The lead screw nut has an external gear 160 
that is in mesh with the helical gear 154. 
Ratchet arms 160A and 160B extend from ratchet arm collars that are mounted 
on the bushings 118A and 118B respectively through roller clutches 164A 
and 164B. The ratchet arms 160A and 160B have cam follower bearings 168A, 
168B at their free ends. The cam follower bearings 168 run in the slot 110 
between the cam tracks 96. Lugs 172 project from the respective ratchet 
arm collars in the opposite direction to the respective ratchet arms. 
Referring to FIGS. 7 and 8, each shell 90A, 90B of the housing 44 is formed 
with two internally threaded bores 176 and 178 and a cartridge 180, having 
a spring-loaded rod 182 captive therein, is fitted in the bore 176. The 
rods 182 engage the lugs 172 and bias the arms 160 to the positions in 
which the cam follower bearings 168A, 168B run against the two cam tracks 
96A, 96B respectively. 
In the following description of the transmission of drive from the feed 
collet 52 to the lead screw nut 158, references to the direction of 
rotation of an element about the axis of the feed shaft 114 relate to the 
element when seen in the direction of the arrow 150 in FIG. 6. 
The clutch 122A allows counter-clockwise rotation of the bushing 118A 
relative to the housing 44, but prevents clockwise rotation of the bushing 
118A. Conversely, the clutch 122B permits clockwise rotation of the drive 
bushing 118B but prevents counter-clockwise rotation of the drive bushing 
118B. 
The clutch 164A allows the ratchet arm 160A to rotate clockwise relative to 
the drive bushing 118, but prevents counter-clockwise rotation of the 
ratchet arm 160A relative to the bushing 118A. Similarly, the clutch 164B 
allows the ratchet arm 160B to rotate in the counter-clockwise direction 
relative to the bushing 118B, but prevents clockwise rotation of the 
ratchet arm 160B relative to the bushing 118B. 
In operation of the boring machine, the feed shaft 114 is moved to one 
axial position or the other, depending upon the desired feed direction, 
and power is supplied to the rotational drive assembly. As the boring bar 
rotates, the feed collet 52 also rotates, and rotational movement of the 
feed collet is converted to a rocking motion of the ratchet arms about the 
axis of the feed shaft 114 as the rods 182 urge the bearings 168A, 168B 
against the tracks 96A, 96B respectively. 
If, for example, the feed shaft is moved to the position in which the dowel 
pin 138A engages the slot 134A of the drive bushing 118A, the rocking 
motion of the ratchet arm 160A is coupled to the feed shaft 114 and the 
feed shaft rotates in the counter-clockwise direction in stepwise fashion. 
Reverse rotation due to any torque that might be applied to the feed shaft 
is prevented by the clutch 164A. Similarly, if the feed shaft is moved to 
the position in which the dowel pin 138B engages the slot 134B in the 
drive bushing 118B, the feed shaft rotates stepwise in the clockwise 
direction. The gears 154, 160 convert rotation of the feed shaft 114 to 
rotation of the lead screw nut 158. Consequently, the axial feed assembly 
is displaced toward (or away from) the rotational drive assembly, 
depending on the position of the shaft 114. 
A feed rate control screw 186 is fitted in the bore 178 of each shell of 
the housing 44. The feed rate control screw 186 projects at its inner end 
toward the lug of the corresponding ratchet arm, and is provided at its 
outer end with a knurled head. A compression spring 192 ensures that the 
feed rate control screw 186 does not turn due to vibration. The screw 186 
is hollow, and a plunger 194 is slidably fitted inside the screw. The lug 
172 limits movement of the plunger 194 into the housing 90, and a snap 
ring 200 on the pin limits its movement out of the housing. Engagement of 
the lug 172 against plunger 194 limits the range of angular movement of 
the ratchet arm under the bias applied through the pin 182. When the screw 
186 is advanced into the housing, the inner end of the plunger 194 engages 
the lug of the ratchet arm and tilts the ratchet arm away from its bias 
position. This reduces the angular travel of the ratchet arm and 
consequently the angle through which the feed shaft 114 rotates on each 
stroke of the ratchet arm. Similarly, when the screw 186 is retracted, it 
allows a greater angular travel of the ratchet arm. In this manner, the 
axial feed rate in the direction controlled by the particular feed rate 
control screw is adjustable. Since the two feed rate control screws are 
independently adjustable, the feed rates in the two possible feed 
directions are themselves independently adjustable. 
Referring to FIG. 2, two feed stops 204F, 204R are mounted on the lead 
screw 48 so that the axial feed assembly is between the two feed stops. 
Each feed stop 204 includes a ring 208 that is internally threaded, so 
that the feed stop can be moved to a desired position along the lead screw 
by rotation about the lead screw, and an arm 212 that projects radially 
from the ring. 
For movement of the axial feed assembly toward the workpiece, the feed stop 
204F is active, whereas for movement away from the workpiece, the feed 
stop 204R is active. As the axial feed assembly is displaced along the 
lead screw, and the tool head moves through the workpiece, the axial feed 
assembly moves toward the active feed stop. When the axial feed assembly 
reaches the active feed stop arm, the plunger 194 engages the arm 212 of 
the active feed stop and is displaced longitudinally relative to the 
housing 44. The inner end of the plunger 194 engages the lug 172 that 
projects from the ratchet arm, and thereby forces the ratchet arm to pivot 
against the bias applied by the pin 182, reducing the feed rate. Over 
several strokes of the ratchet arm, the action of the plunger 194 against 
the lug 172 reduces the feed rate to zero. The drive connection between 
the feed collet 52 and the lead screw nut 158 is thereby disengaged, and 
further axial movement of the boring bar is prevented. This ensures that 
the feed range of the boring machine is properly limited, and avoids 
damage to the boring machine and to the workpiece. 
It will be appreciated that the invention is not restricted to the 
particular embodiment that has been described, and that variations may be 
made therein without departing from the scope of the invention as defined 
in the appended claims and equivalents thereof.