Bayonet tool locking device

A device for locking a tool to a cutting machine. During a locking action a drawbar is rotated to bring a radial lock pin into registry with oppositely directed bayonet slots formed in a tool that has been inserted into a pocket in the end face of a tool holder; a spring acts on the drawbar to move the lock pin into the bayonet slots. The lock pin is carried on a nose element that is threaded onto the drawbar for drawing the lock pin toward the drawbar to achieve an axial lock force between the tool and the tool holder. Tapered frusto-conical surfaces on the tool and holder produce a self-centering tapered sticking lock action. The oppositely directed bayonet slots allow the tool to be forceably dislodged from the sticking taper when the drawbar is rotated in a reverse direction.

BACKGROUND AND SUMMARY 
This invention relates to a device for locking a cutting tool machine. The 
locking device is similar in some respects to locking devices shown in 
U.S. Pat. No. 3,118,345to Bullard et al, U.S. Pat. No. 3,311,024 to J. 
Daugherty, U.S. Pat. No. 3,730,637 to V. Cellini, U.S. Pat. No. 4,758,122 
to H. Kubo, and U.S. Pat. No. 4,906,147 to Friesinger et al. 
The locking device of the present invention is designed to achieve a secure 
locking of the tool to the cutting machine, with a relatively strong axial 
holding force; a screw thread frictional force augments the axial lock 
force. The tool is received within an axially-extending pocket in the 
exposed face of a holder that forms part of the machine; a bayonet lock 
system is combined with a threaded puller (clamping) mechanism to securely 
retain the tool against axial dislocation out of the pocket. Radial and 
circumferential loads are transmitted from the tool directly to the 
holder. Axial loads are transmitted from the tool through the threaded 
clamping mechanism to the holder; the clamping mechanism is required to 
handle only the axial loads. 
During the process of locking the tool to the holder a drawbar is rotated 
to cause a lock pin to enter into a bayonet slot means carried by the 
tool. Rotation of the drawbar moves the pin into the blind end of the 
bayonet slot, after which a nose piece has a screw motion along the 
drawbar to pull the lock pin axially so as to produce an axial clamp 
action between the tool and holder. The tool has a tapered shank that 
wedges into the holder to provide a very secure connection between the 
tool and holder. To unlock the tool from the holder the drawbar is rotated 
in a reverse direction so that the nose piece has a reverse screw travel 
along the drawbar; the lock pin exerts an axial force on the tool to 
unseat it from the holder.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION 
The drawings show a holder 11 of a conventional cutting machine. In the 
illustrated arrangement the cutting machine is a turret lathe; holder 11 
is a stationary non-rotating part of the machine. At its left end holder 
11 is formed with a pocket 13 that is adapted to receive a tool assembly 
15. 
The illustrated tool assembly 15 comprises a tool body 16 and tool 
connector 17. The connector is threaded into the tool body at 18, after 
which a set screw 19 is installed to rigidly hold the tool assembly 
together. For present purposes, tool body 16 and tool connector 17 
constitute a single tool that can be moved between a locked position 
securely mounted in (on) holder 11, and an unlocked position separated 
from holder 11. The primary object of the present invention is to provide 
a tool locking mechanism that can be expeditiously operated to securely 
lock the tool to holder 11 or unlock the tool from holder 11. 
Projecting from the end face of holder Il is a locator pin 21. Tool body 16 
has a mating hole in its end face adapted to fit onto pin 21 to prevent 
the tool from rotating relative to holder 11 during the locking or 
unlocking process. The primary locking force is provided by a tapered 
shank surface 22 on tool body 16 and a mating tapered bore surface 24 
formed at the mouth of pocket 13 in holder 11. Tapered surfaces 22 and 24 
are frusto-conical surfaces having similar taper angles of about three 
degrees. When tool assembly 15 is pulled axially into holder 11 the 
tapered surfaces lock together in a wedged condition, thereby providing a 
secure locking of the tool assembly in the holder. 
A rotary drawbar 27 extends within holder 11 for independent rotation 
around holder axis 29 when the locking device is in the process of locking 
the tool to holder 11 or unlocking the tool from holder 11; rotation of 
the drawbar in one direction effects a tool lock action, and rotation of 
the drawbar in the opposite direction produces a tool unlock action. 
A hexagonal socket 28 in the right end face of the drawbar is adapted to 
receive a hexagonal turning implement (allen wrench) for achieving a 
rotary motion of the drawbar. 
As shown in FIG. 1, the drawbar extends leftwardly through a large diameter 
axial bore 31 in holder 11 into a reduced diameter connecting bore 33 
formed between bore 31 and aforementioned pocket 13. The juncture between 
bores 31 and 33 forms an annular radial shoulder 35. The drawbar is 
floatably mounted within holder 11 so that the drawbar can rotate within 
holder 11 and also move axially toward or away from pocket 13. 
The drawbar is formed with a large diameter section 39 and a small diameter 
section 41. A coil spring 43 encircles section 41 of the drawbar between 
retainer nut 37 and a washer 45 carried on the drawbar so as to exert a 
leftward biasing force on drawbar section 39. Washer 45 is rotatably 
seated against radial surface 47 of the drawbar so that the drawbar can 
rotate without transmitting a significant rotational distortional force to 
the spring; during rotational movement of the drawbar radial surface 47 
has rotary slidable motion on washer 45. 
At its left end the drawbar is threaded to mate with internal threads 
formed on a nose element 49. A radial lock pin 51 extends transversely 
through the nose element to mate with bayonet slots 53 formed in an 
annular section 54 of tool connector portion 17. A sleeve 56 is press fit 
onto annular section 54. 
As shown in FIG. 1, lock pin 51 extends in the plane of the paper 
transverse to the bayonet slots 53. FIG. 3 shows lock pin 51 extending 
within the bayonet slots. Rotation of the drawbar provides the impetus for 
moving the lock pin to a position in registry with the bayonet slots. As 
the drawbar rotates to a position where lock pin 51 is transverse to the 
plane of the paper, spring 43 moves the drawbar and attached nose element 
49 leftwardly to force pin 51 into the FIG. 3 position within the bayonet 
slots. 
A sleeve 57 is rotatably (swivably) mounted within holder 11 in surrounding 
relation to drawbar 27. Two axial slot sections 59 are formed in the 
sleeve to accommodate the ends of a radial connector pin 61 extending 
through the drawbar. A circumferential slot section 63 is connected to 
each axial slot section 59 so that when the drawbar is in the FIG. 3 
position connector pin 61 moves to a position at the left ends of slot 
sections 59, as indicated by numeral 66 in FIG. 2. Each axial slot section 
59 and connected circumferential slot section 63 forms an L-shaped slot. 
FIG. 2 shows one of the L-shaped slots in full lines. The other L-shaped 
slot is shown partially, using dotted lines. The two L-shaped slots are 
similar except that the circumferential slot sections extend in opposite 
directions, whereby when pin 61 is in the FIG. 3 position it can rotate 
around drawbar axis 29 so that its ends move freely within circumferential 
slot sections 63 for a limited rotational distance. When the drawbar is in 
the FIG. 1 position connector pin 61 extends into axial slot sections 59, 
such that sleeve 57 and drawbar 27 are rotatable as a unit. Sleeve 57 has 
an inwardly-radiating flange 65 in axial registry with aforementioned 
shoulder 35 and drawbar radial surface 67. 
FIG. 1 represents the unlocked condition of the device, with tool assembly 
15 inserted loosely into pocket 13 to compress spring 43. To achieve a 
locking action drawbar 27 is rotated so that lock pin 51 registers with 
the bayonet slots 53. Spring 43 then moves the drawbar and nose element 49 
leftwardly so that pin 51 moves into the bayonet slots (as shown in FIG. 
3). Continued rotation of the drawbar enables pin 51 to move into the 
blind ends 65 of the bayonet slots; at this time connector pin 61 is in 
the position designated by numeral 66 (FIG. 2). When lock pin 51 reaches 
the blind ends of the bayonet slots nose element 49 stops rotating 
(because pin 21 prevents rotation of the tool assembly). However drawbar 
27 continues to rotate, such that nose element 49 shifts slightly to the 
right because of its threaded connection with the drawbar. The thread 
action produces a pressure engagement between tapered shank surface 22 of 
the tool and tapered bore surface 24 on holder 11. At the same time the 
thread action causes drawbar 27 to be drawn slightly to the left so that 
sleeve flange 68 is squeezed between shoulder 35 and drawbar radial 
surface 67. This squeezing action brings the drawbar gradually to a 
stopped position. 
Sleeve 57 and its radial flange 68 have pressure contact with surface 35 to 
bring the assembly to a tool-clamped condition in which the tool has axial 
pressure engagement with tapered surface 24; the tapered surfaces act to 
center the tool relative to holder 11. 
To effect an unlocking action the drawbar is rotated in the reverse 
direction. Initially, connector pin 61 moves into circumferential slot 
sections 63 from axial slot sections 59; at the same time nose element 49 
may experience a slight leftward unthreading action on the drawbar threads 
to reduce the squeeze pressure of surfaces 35 and 67 on sleeve flange 68. 
Slot sections 63 enable the drawbar to be turned a slight distance without 
having to rotate nose element 49; as the squeeze pressure on sleeve flange 
68 is reduced nose element 49 is rotated so that pin 51 moves from the 
circumferential portions of bayonet slots 53 into the axial portions of 
the bayonet slots (as depicted in FIG. 4). Tool assembly 16 cannot rotate 
(because of the action of pin 21); reverse rotation of drawbar 27 
therefore causes nose element 49 to partially unthreaded from the drawbar. 
The nose element shifts leftwardly (in FIG. 3) to cause pin 51 to push the 
tool away from holder 11. The unthreading motion of nose element 49 along 
drawbar 27 acts as a positive force to cause tapered surfaces 22 and 24 to 
be disengaged from each other. 
The threaded connection between nose element 49 and drawbar 27 provides a 
mechanical advantage, whereby a relatively small wrench force (applied to 
socket 28) can produce a relatively strong locking/unlocking force between 
tapered surfaces 22 and 24. 
The drawings shows the bayonet slots on tool assembly 15, and lock pin 51 
on nose element 49. However, the reverse arrangement could be used, i.e. 
the lock pin could be formed on the tool assembly and the bayonet slots 
could be formed on the nose element. Some structural redesign would be 
required.