# Patent

## Title
Bit retention assembly for rotary hammer

## Abstract

A rotary hammer includes a motor, a spindle coupled to the motor for receiving torque from the motor, a piston at least partially received within the spindle for reciprocation therein, and an anvil received within the spindle for reciprocation in response to reciprocation of the piston. The anvil imparts axial impacts to a tool bit in response to reciprocation of the piston. The rotary hammer also includes a bit retention assembly for securing the tool bit to the spindle. The bit retention assembly includes a collar with an indicator thereon. The indicator is at least partially visible to a user of the rotary hammer when the tool bit is improperly inserted within the spindle.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to U.S. Provisional Patent Application No. 61/597,542 filed on Feb. 10, 2012, the entire content of which is incorporated herein by reference.


FIELD OF THE INVENTION
The present invention relates to rotary power tools, and more particularly to bit retention assemblies for rotary power tools.
BACKGROUND OF THE INVENTION
Rotary hammers typically include a rotatable spindle, a reciprocating piston within the spindle, and a striker that is selectively reciprocable within the piston in response to an air pocket developed between the piston and the striker. Rotary hammers also typically include an anvil that is impacted by the striker when the striker reciprocates within the piston. The impact between the striker and the anvil is transferred to a tool bit, causing it to reciprocate for performing work on a work piece. Rotary hammers further include bit retention assemblies for securing a tool bit within the spindle.
SUMMARY OF THE INVENTION
The invention provides, in one aspect, a rotary hammer adapted to impart axial impacts to a tool bit. The rotary hammer includes a motor, a spindle coupled to the motor for receiving torque from the motor, a piston at least partially received within the spindle for reciprocation therein, and an anvil received within the spindle for reciprocation in response to reciprocation of the piston. The anvil imparts axial impacts to the tool bit in response to reciprocation of the piston. The rotary hammer also includes a bit retention assembly for securing the tool bit to the spindle. The bit retention assembly includes a collar with an indicator thereon. The indicator is at least partially visible to a user of the rotary hammer when the tool bit is improperly inserted within the spindle.
Other features and aspects of the invention will become apparent by consideration of the following detailed description and accompanying drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view of a rotary hammer of the invention.
FIG. 2 is a cross-sectional view of one embodiment of a bit retention assembly for use with the rotary hammer of FIG. 1, illustrating a tool bit properly inserted within a spindle of the rotary hammer.
FIG. 3 is a cross-sectional view of the bit retention assembly of FIG. 2, illustrating the tool bit improperly inserted within the spindle.
FIG. 4 is a cross-sectional view of the bit retention assembly of FIG. 2, illustrating a tool bit having a different configuration than that shown in FIG. 2 properly inserted within the spindle.
FIG. 5 is a cross-sectional view of the bit retention assembly of FIG. 2, illustrating the tool bit of FIG. 4 improperly inserted within the spindle.
FIG. 6 is a cross-sectional view of the rotary hammer along line 6-6 in FIG. 5.
FIG. 7 is a perspective view of a collar of the bit retention assembly shown in a rearward position corresponding with the improper insertion of the tool bit within the spindle as shown in FIG. 5.
FIG. 8 is a cross-sectional view of another embodiment of a bit retention assembly for use with the rotary hammer of FIG. 1, illustrating a tool bit being inserted within a spindle of the rotary hammer.
FIG. 9 is a cross-sectional view of the bit retention assembly of FIG. 8, illustrating continued insertion of the tool bit within the spindle.
FIG. 10 is a cross-sectional view of the bit retention assembly of FIG. 8, illustrating the tool bit being fully inserted within the spindle.
FIG. 11 is a cross-sectional view of the bit retention assembly of FIG. 8, illustrating a collar of the bit retention assembly being moved to a rearward position to permit removal of the tool bit from the spindle.



Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
DETAILED DESCRIPTION
FIG. 1 illustrates a rotary hammer 10 including a housing 14, a motor 18 disposed within the housing 14, and a rotatable spindle 22 coupled to the motor 18 for receiving torque from the motor 18. A tool bit 26a, 26b may be secured to the spindle 22 for co-rotation with the spindle 22 (e.g., using a spline-fit or a hexagonal-fit). As is described in more detail below, the rotary hammer 10 also includes a bit retention assembly 30 coupled for co-rotation with the spindle 22 to facilitate quick removal and replacement of different tool bits 26a, 26b. When a tool bit 26a having a splines 34 is inserted within the spindle 22 for co-rotation therewith, a necked section or groove 38 (FIG. 2) around the periphery of the tool bit shank is engaged by the bit retention assembly 30 to axially retain the tool bit 26a to the spindle 22. Alternatively, when a tool bit 26b having a hexagonal outer periphery 42 is inserted within the spindle 22 for co-rotation therewith, a single cut or recessed flat 46 (FIG. 4) coinciding with one of the surfaces of the hexagonal tool bit shank is engaged by the bit retention assembly 30 to axially retain the tool bit 26b to the spindle 22. With both tool bits 26a, 26b, the bit retention assembly 30 constrains axial movement of the tool bits 26a, 26b relative to the spindle 22 to the lengths of the groove 38 and the recessed flat 46, respectively.
With reference to FIG. 1, the motor 18 is powered by a remote power source (e.g., a household electrical outlet) through a power cord 50. Alternatively, the motor 18 may be configured as a DC motor that receives power from an on-board power source (e.g., a battery). The battery may include any of a number of different nominal voltages (e.g., 12V, 18V, etc.), and may be configured having any of a number of different chemistries (e.g., lithium-ion, nickel-cadmium, etc.). The motor 18 is selectively activated by depressing a trigger 54 which, in turn, actuates a switch (not shown). The switch may be electrically connected to the motor 18 via a top-level or master controller, or one or more circuits, for controlling operation of the motor 18.
With continued reference to FIG. 1, the rotary hammer 10 further includes a transmission 58 for transferring torque from the motor 18 to the spindle 22 and an impact mechanism 62 driven by the transmission 58 for delivering repeated impacts to the tool bit 26a, 26b for performing work on a workpiece. In the illustrated embodiment, the impact mechanism 62 includes a reciprocating piston 66 disposed within the spindle 22, a striker 70 that is selectively reciprocable within the spindle 22 in response to reciprocation of the piston 66, and an anvil 74 that is impacted by the striker 70 when the striker 70 reciprocates toward the tool bit 26a, 26b. More specifically, an air pocket is developed between the piston 66 and the striker 70 when the piston 66 reciprocates within the spindle 22, whereby expansion and contraction of the air pocket induces reciprocation of the striker 70. The impact between the striker 70 and the anvil 74 is then transferred to the tool bit 26a, 26b, causing it to reciprocate for performing work on the workpiece.
FIGS. 2-7 illustrate one embodiment of a bit retention assembly 30 for use with the rotary hammer 10 of FIG. 1. The bit retention assembly 10 includes a rear collar 78 that is axially displaceable along the spindle 22 against the bias of a spring 82 between a forward position (FIG. 2) and a rearward position (FIG. 3), and a cylindrical pin 86 that is maintained within a slot 90 formed in the spindle 22 (FIGS. 2-5). The slot 90 extends between an exterior of the spindle 22 and a receptacle 94 in which the tool bit 26a, 26b is inserted. The pin 86 is oriented transversely to the spindle 22 and maintained between two adjacent washers 98, 102. The pin 86 is also coupled to the collar 78 for axial displacement therewith, such that rearward movement of the pin 86 within the slot 90 (from the frame of reference of FIG. 2) also causes the collar 78 to move rearward with respect to the spindle 22. The pin 86 is biased within the slot 90 to the position shown in FIG. 2 by the spring 82 and the washer 98. In this position, the pin 86 at least partially protrudes into the receptacle 94 when the collar 78 is in its forward position shown in FIG. 2.
With continued reference to FIGS. 2-5, the bit retention assembly 30 also includes a retaining ring 106 and a front collar 110 coupled for co-rotation with the spindle 22 between which the remaining components of the bit retention assembly 30 are secured. The front collar 110 is positioned forward of the rear collar 78 for limiting axial movement of the rear collar 78 in a forward direction, and includes a circumferential lip 114 surrounding a front portion of the rear collar 78.
To properly or fully insert the splined tool bit 26a within the spindle 22, the tool bit 26a may be inserted within the spindle 22 without separately pushing the collar 78 against the bias of the spring 82, causing the rear of the tool bit 26a to engage the pin 86 and push it rearward against the bias of the spring 82. As the pin 86 and the collar 78 are pushed rearward by continued insertion of the tool bit 26a, the pin 86 is also displaced radially outward within the slot 90 (FIG. 3) until the pin 86 clears the end of the tool bit 26a. The pin 86 is then returned to the position shown in FIG. 2 by the spring 82 in response to the pin 86 clearing the end of the tool bit 26a and the splines 34, at which time the pin 86 protrudes into the receptacle 94 and is at least partially received in the groove 38. Thereafter, the tool bit 26a is axially retained within the spindle 22, with the pin 86 constraining the axial reciprocation or stroke of the tool bit 26a during operation of the rotary hammer 10 to the length of the groove 38. The hexagonal tool bit 26b may be properly or fully inserted within the spindle 22 in the same manner, but in addition the tool bit 26b must be properly angularly oriented relative to the spindle 22 such that the recessed flat 46 in the tool bit 26b is aligned with the pin 86.
To release either of the tool bits 26a, 26b from the bit retention assembly 30, the collar 78 is pushed against the bias of the spring 82 to the rearward position shown in FIG. 3, thereby moving with it the washers 98, 102 and the pin 86. The pin 86 is displaced within the slot 90 radially outwardly to a position in which it no longer protrudes into the receptacle 94, thereby allowing the end of the tool bit 26a, 26b to clear the pin 86 for removing the tool bit 26a, 26b from the spindle 22.
Should the splined tool bit 26a be inserted within the spindle 22 an insufficient amount (FIG. 3), or should the hexagonal tool bit 26b be inserted in an orientation in which the pin 86 is misaligned with the recessed flat 46 (FIG. 5), both of which instances being considered “improper” insertion of the tool bit 26a, 26b within the spindle 22, interference between the tool bit 26a, 26b and the pin 86 will inhibit the pin 86 from being returned to either of the positions shown in FIG. 2 or 4. Rather, the pin 86 would wedge within the slot 90 to prevent the collar 78 from returning to its normal operating or forward position shown in FIGS. 2 and 4. A front portion of the collar 78 includes an indicator 118 (e.g., a red stripe) on its outer peripheral surface (FIG. 7), which is exposed and visible to the user of the rotary hammer 10 when the collar 78 is maintained in its rearward position by the wedged pin 86, to indicate to the user the tool bit 26a, 26b is not fully secured by the bit retention assembly 30. The indicator 118 is otherwise covered or shrouded by the lip 114 of the front collar 110, and hidden from view of the user, when the tool bit 26a, 26b is fully and properly secured by the bit retention assembly 30 as shown in FIGS. 2 and 4.
FIGS. 8-11 illustrate another embodiment of a bit retention assembly 204 for use with the rotary hammer 10 of FIG. 1. With reference to FIG. 8, the hammer 10 includes a rotatable spindle 208 and an anvil 212 that is impacted by a reciprocating striker (FIG. 1). The impact between the striker and the anvil 212 is transferred to a splined tool bit 216, causing it to reciprocate for performing work on a workpiece. The bit retention assembly 204 includes a collar 220 that is axially displaceable along the spindle 208 against the bias of a spring 224 and opposed latches 228 that are displaceable within respective slots 232 in the spindle 208. The bit retention assembly 204 also includes a washer 236 positioned between the spring 224 and the collar 220. The inner portion of the washer 236 is also received within a recess 240 in the respective latches 228, such that displacement of the washer 236 results in displacement of the latches 228 within the slots 232.
The bit retention assembly 204 further includes a fixed or stationary front collar 248, a dust shield 252 adjacent a front edge of the front collar 2148, and a washer 256 adjacent an annular step 260 on an internal periphery of the front collar 248 (FIGS. 8-11). The front collar 248 is trapped or held stationary in an axial direction relative to the spindle 208 by the dust shield 252 and the washer 256. The bit retention assembly 204 also includes an inner locking sleeve 264 surrounding at least a front portion of each of the slots 232. The sleeve 264 limits the radially outward extent to which each of the latches 228 may be displaced during insertion of the tool bit 216 (FIG. 9), described in more detail below. The bit retention assembly 204 further includes a lock ring 268 secured to the spindle 208, a washer 272 adjacent the lock ring 268, and two O-rings 276 positioned between the washers 260, 272. When installed, the O-rings 276 may be slightly compressed between the washers 260, 272 for exerting a biasing force against the washer 260 and the locking sleeve 264 for maintaining the locking sleeve 264 in the position shown in FIGS. 8-11.
To secure the tool bit 216 within the bit retention assembly 204, the tool bit 216 is inserted within the spindle 208, causing the rear of the tool bit 216 to engage the latches 228 to push them rearward against the bias of the spring 224. As the latches 228 are pushed rearward by the tool bit 216, the latches 228 are also displaced radially outwardly within the respective slots 232 until the latches 228 clear the end of the tool bit 216 (FIG. 9). The latches 228 are returned to the position shown in FIG. 10 by the spring 224 and the washer 236 in response to the latches 228 clearing the end of the tool bit 216, at which time the latches 228 are at least partially received in corresponding grooves 244 of the tool bit 216 to define the extent to which the tool bit 216 may reciprocate within the spindle 208. To release the tool bit 216 from the bit retention assembly 204, the collar 220 is pushed rearward, thereby moving with it the washer 236 and the latches 228 against the bias of the spring 224 (FIG. 11). The latches 228 are displaced within the respective slots 232 radially outwardly to permit the end of the tool bit 216 to clear the latches 228, thereby allowing the tool bit 216 to be removed from the spindle 208.
When the rotary hammer with the bit retention assembly 204 transitions from an “impact” mode in which impacts from the anvil 212 are transferred to the tool bit 216, to an “idle” mode in which the anvil 212 is parked or brought to rest within the spindle 208, the bit 216 may exert a final impact on the latches 228 which, in turn, may be transferred to the locking sleeve 264. The impact on the locking sleeve 264 is cushioned by the O-rings 276, which are compressed slightly to permit the locking sleeve 264 to move forwardly with the latches 228 as the latches 228 and locking sleeve 264 decelerate. A front edge 280 of the rear collar 220 also contacts the washer 256. Therefore, as the O-rings 276 are compressed while absorbing the final impact on the tool bit 216, the rear collar 220 is also permitted to move forwardly a small amount with the latches 228 and the locking sleeve 264. As such, substantially no relative movement occurs between the latches 228, the locking sleeve 264, and the rear collar 220 while the O-rings 276 cushion the final impact on the tool bit 216, thereby reducing any reaction forces exerted on the latches 228 at this time. Alternatively, the O-rings 276 may have any of a number of different cross-sectional shapes, or may further be replaced by one or more compression springs.
Various features of the invention are set forth in the following claims.

## Claims

1. A rotary hammer adapted to impart axial impacts to a tool bit, the rotary hammer comprising:
a motor;
a spindle coupled to the motor for receiving torque from the motor;
a piston at least partially received within the spindle for reciprocation therein;
an anvil received within the spindle for reciprocation in response to reciprocation of the piston, the anvil imparting axial impacts to the tool bit in response to reciprocation of the piston; and
a bit retention assembly for securing the tool bit to the spindle, the bit retention assembly including
a front collar held stationary in both forward and rearward axial directions relative to the spindle and having a circumferential lip, and
a rear collar with an indicator thereon that is movable with the rear collar, the indicator being unshrouded by the circumferential lip and at least partially visible to a user of the rotary hammer when the tool bit is improperly inserted within the spindle.

2. The rotary hammer of claim 1, wherein the spindle includes
a receptacle in which the tool bit is received, and
a slot extending between an exterior of the spindle and the receptacle.

3. The rotary hammer of claim 2, wherein the bit retention assembly further includes
a spring biasing the rear collar toward a first axial position in which the indicator is shrouded from view, and
a pin that is maintained within the slot and at least partially protruding into the receptacle when the rear collar is in the first axial position.

4. The rotary hammer of claim 3, wherein the bit retention assembly further includes a washer positioned between the spring and the pin.

5. The rotary hammer of claim 4, wherein the washer is a first washer, wherein the bit retention assembly includes a second washer, and wherein the pin is maintained between the first and second washers.

6. The rotary hammer of claim 5, wherein the second washer is engaged with the rear collar.

7. The rotary hammer of claim 4, wherein the pin is biased to a position in which at least a portion of the pin protrudes into the receptacle by the spring and the washer when the rear collar is in the first axial position.

8. The rotary hammer of claim 4, wherein the bit retention assembly further includes a retaining ring coupled to the spindle, and wherein the spring is positioned between the washer and the retaining ring.

9. The rotary hammer of claim 3, wherein the pin is oriented transversely to the tool bit.

10. The rotary hammer of claim 3, wherein the pin is prevented from protruding into the receptacle by the tool bit when the tool bit is improperly inserted into the spindle.

11. The rotary hammer of claim 10, wherein, when the pin is prevented from protruding into the receptacle, the rear collar is prevented by the pin from moving from a second axial position, in which the indicator is exposed and therefore visible to a user of the rotary hammer, to the first axial position.

12. The rotary hammer of claim 11, wherein the tool bit includes a groove in which the pin is received when the tool bit is properly inserted within the spindle.

13. The rotary hammer of claim 11, wherein the tool bit includes a recessed flat in which the pin is received when the tool bit is properly inserted within the spindle.

14. The rotary hammer of claim 11, wherein the rear collar is moved from the first axial position to the second axial position in response to insertion of the tool bit within the spindle.

15. The rotary hammer of claim 1, wherein the indicator is positioned on an outer peripheral surface of the rear collar.

16. The rotary hammer of claim 15, wherein the front collar is positioned forward of the rear collar for limiting axial movement of the rear collar in a forward direction, and wherein the circumferential lip surrounds a front portion of the rear collar.

17. The rotary hammer of claim 16, wherein the indicator is shrouded by the lip when the tool bit is properly inserted within the spindle and the rear collar is in a first axial position.

18. The rotary hammer of claim 17, wherein the indicator is unshrouded by the lip, and therefore visible to a user of the rotary hammer, when the tool bit is improperly inserted within the spindle and the rear collar is in a second axial position.

19. The rotary hammer of claim 1, wherein the indicator is a red stripe.

20. The rotary hammer of claim 1, further comprising a striker received within the spindle for reciprocation in response to reciprocation of the piston, wherein the anvil is positioned between the striker and the tool bit.