GB2407851A - Slip clutch for rotary power tool - Google Patents

Slip clutch for rotary power tool Download PDF

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Publication number
GB2407851A
GB2407851A GB0325879A GB0325879A GB2407851A GB 2407851 A GB2407851 A GB 2407851A GB 0325879 A GB0325879 A GB 0325879A GB 0325879 A GB0325879 A GB 0325879A GB 2407851 A GB2407851 A GB 2407851A
Authority
GB
United Kingdom
Prior art keywords
clutch
clutch member
spindle
relative
engaging portions
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB0325879A
Other versions
GB0325879D0 (en
Inventor
Manfred Droste
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Black and Decker Inc
Original Assignee
Black and Decker Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Black and Decker Inc filed Critical Black and Decker Inc
Priority to GB0325879A priority Critical patent/GB2407851A/en
Publication of GB0325879D0 publication Critical patent/GB0325879D0/en
Priority to EP04008739A priority patent/EP1468789A3/en
Priority to US10/825,838 priority patent/US7216749B2/en
Publication of GB2407851A publication Critical patent/GB2407851A/en
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D7/00—Slip couplings, e.g. slipping on overload, for absorbing shock
    • F16D7/04—Slip couplings, e.g. slipping on overload, for absorbing shock of the ratchet type
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25B—TOOLS OR BENCH DEVICES NOT OTHERWISE PROVIDED FOR, FOR FASTENING, CONNECTING, DISENGAGING OR HOLDING
    • B25B23/00—Details of, or accessories for, spanners, wrenches, screwdrivers
    • B25B23/14—Arrangement of torque limiters or torque indicators in wrenches or screwdrivers
    • B25B23/141—Mechanical overload release couplings
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25D—PERCUSSIVE TOOLS
    • B25D16/00—Portable percussive machines with superimposed rotation, the rotational movement of the output shaft of a motor being modified to generate axial impacts on the tool bit
    • B25D16/003—Clutches specially adapted therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25F—COMBINATION OR MULTI-PURPOSE TOOLS NOT OTHERWISE PROVIDED FOR; DETAILS OR COMPONENTS OF PORTABLE POWER-DRIVEN TOOLS NOT PARTICULARLY RELATED TO THE OPERATIONS PERFORMED AND NOT OTHERWISE PROVIDED FOR
    • B25F5/00—Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for
    • B25F5/001—Gearings, speed selectors, clutches or the like specially adapted for rotary tools
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D43/00—Automatic clutches
    • F16D43/02—Automatic clutches actuated entirely mechanically
    • F16D43/20—Automatic clutches actuated entirely mechanically controlled by torque, e.g. overload-release clutches, slip-clutches with means by which torque varies the clutching pressure
    • F16D43/202—Automatic clutches actuated entirely mechanically controlled by torque, e.g. overload-release clutches, slip-clutches with means by which torque varies the clutching pressure of the ratchet type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D7/00—Slip couplings, e.g. slipping on overload, for absorbing shock
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D7/00—Slip couplings, e.g. slipping on overload, for absorbing shock
    • F16D7/04—Slip couplings, e.g. slipping on overload, for absorbing shock of the ratchet type
    • F16D7/042—Slip couplings, e.g. slipping on overload, for absorbing shock of the ratchet type with at least one part moving axially between engagement and disengagement
    • F16D7/044—Slip couplings, e.g. slipping on overload, for absorbing shock of the ratchet type with at least one part moving axially between engagement and disengagement the axially moving part being coaxial with the rotation, e.g. a gear with face teeth
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D7/00—Slip couplings, e.g. slipping on overload, for absorbing shock
    • F16D7/04—Slip couplings, e.g. slipping on overload, for absorbing shock of the ratchet type
    • F16D7/06—Slip couplings, e.g. slipping on overload, for absorbing shock of the ratchet type with intermediate balls or rollers
    • F16D7/08—Slip couplings, e.g. slipping on overload, for absorbing shock of the ratchet type with intermediate balls or rollers moving axially between engagement and disengagement
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D7/00—Slip couplings, e.g. slipping on overload, for absorbing shock
    • F16D7/04—Slip couplings, e.g. slipping on overload, for absorbing shock of the ratchet type
    • F16D7/06—Slip couplings, e.g. slipping on overload, for absorbing shock of the ratchet type with intermediate balls or rollers
    • F16D7/10—Slip couplings, e.g. slipping on overload, for absorbing shock of the ratchet type with intermediate balls or rollers moving radially between engagement and disengagement
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23B—TURNING; BORING
    • B23B2260/00—Details of constructional elements
    • B23B2260/044—Clutches
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25D—PERCUSSIVE TOOLS
    • B25D2250/00—General details of portable percussive tools; Components used in portable percussive tools
    • B25D2250/165—Overload clutches, torque limiters

Landscapes

  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Percussive Tools And Related Accessories (AREA)

Abstract

An overload clutch for a rotary hammer has an external surface of a spindle 4 formed with a series of tapering grooves 104 which become narrower in a direction moving towards the forward end of the spindle 4. A slider sleeve 41 is provided with splines 106 which also taper in a direction towards forward end of the slider sleeve 41 to prevent relative rotation but allow axial movement of the sleeve 41. A spring 56 biases the slider sleeve 41 into engagement with elastomeric O-ring 42, and a spring 47 biases sets of cooperating teeth on a spindle drive gear 40 and slider sleeve 41 into engagement with each other which allows the slider sleeve 41 to rotationally drive the spindle 4 by means of cooperation between the splines 106 on the slider sleeve 41 and the grooves 104 on the sleeve 4. When the torque exceeds a predetermined torque threshold, the teeth on the spindle drive gear 40 and slider sleeve 41 slide over each other, as a result of which the drive gear 40 slides forwardly along the slider sleeve 41 against the action of spring 47 disconnecting the drive. The tool may have a number of drive modes, which may be selected/deselected by moving slider sleeve 41 against spring bias 56.

Description

240785 1
CLUTCH FOR ROTARY POWER TOOL AND ROTARY POWER TOOL
INCORPORATNG SUCH CLUTCH
The present invention relates to a clutch for a rotary power tool, and relates particularly, but not exclusively, to an overload clutch for a handheld power hammer.
The invention also relates to a handheld power hammer incorporating such a clutch.
Rotary hammers are known which have a housing and a hollow cylindrical spindle mounted in the housing. The spindle allows insertion of the shank of a tool or bit, for example a drill bit or a chisel bit, into the front end thereof so that it is retained the front end of the spindle with a degree of axial movement. The spindle may be a single cylindrical part or may be made of two or more cylindrical parts, which together form the hammer spindle. For example, a front part of the spindle may be formed as a separate tool holder body for retaining the tool or bit. Such hammers are generally provided with an impact mechanism which converts the rotational drive from an electric motor to a reciprocating drive causing a piston, which may be a hollow piston, to reciprocate within the spindle. The piston reciprocatingly drives a ram by means of a closed air cushion located between the piston and the ram. The impacts from the ram are then transmitted to the tool or bit of the hammer, optionally via a beatpiece.
Some hammers can be employed in combination impact and drilling mode or in a drilling only mode in which the spindle, or a forwardmost part of the spindle, and hence the bit inserted therein will be caused to rotate. In the combination impact and drilling mode the bit will be caused to rotate at the same time as the bit receives repeated impact. Such hammers generally also have a hammer only mode in which the spindle is locked against rotation.
Rotary hammers are known to have overload clutches in the drive train which transmits rotary drive from the motor to the spindle, or forwardmost part of the spindle.
Such overload clutches are designed to transmit rotary drive when the transmitted drive torque is below a predetermined threshold and to slip when the transmitted drive torque exceeds the threshold. During rotary hammering or drilling, when working on materials of non-uniform hardness, for example aggregate or steel reinforced concrete, the bit can become stuck, which causes the torque transmitted via the rotary drive train to increase and causes the hammer housing to tend to rotate against the grip of the user. The torque can increase rapidly and in some cases the user can lose control of the hammer P-UK-PR11 1 6B : and be injured. The use of an overload clutch can reduce the risk of this incurring, by ensuring that the clutch slips and rotary drive to the bit is interrupted at a torque threshold below that where a user is likely to lose control of the hammer. Accordingly, the clutch must slip reliably at a predetermined torque throughout the lifetime of the hammer, even after sustained use of the hammer.
An overload clutch of this type is disclosed in EP 0552328, in which a pair of cooperating ratchet plates are urged into engagement with each other by a compression spring. When a predetermined threshold torque is exceeded, for example as a result of the drill bit becoming stuck in a workpiece, the ratchet plates can slip relative to each other against the action of the spring. However, known overload clutches of this type suffer from the drawback that at very high torque levels, the ratchet plates can be moved rapidly out of engagement with each other to the extremities of their permitted relative movement and then move rapidly back into engagement with each other, causing problems in controlling the tool.
Preferred embodiments of the present invention seek to overcome the above
disadvantages of the prior art.
According to an aspect of the present invention, there is provided a clutch for a rotary power tool having a housing, a spindle rotatably mounted within the housing, and a motor for causing rotation of said spindle about a first axis, the clutch comprising: a first clutch member adapted to be mounted to said spindle and to rotate therewith and slide relative thereto in a direction substantially parallel to said first axis, said first clutch member having at least one first friction surface inclined in use relative to said first axis for engaging a respective corresponding second friction surface on said spindle as a result of movement of said first clutch member relative to the spindle; first biasing means adapted to act between said spindle and said first clutch member for biasing said first clutch member towards a stop; a second clutch member having a first condition in which said second clutch member engages said first clutch member and rotates therewith, and a second condition in which said second clutch member can move relative to said first clutch member; and second biasing means adapted to act between said first and second clutch members for urging said second clutch member towards said first condition.By providing a first clutch member having at least one first friction surface inclined relative P-UK-PR11 1 6B to the first axis for engaging a respective corresponding second friction surface on the spindle, this provides the advantage of providing a reaction force, from the or each corresponding second friction surface on the spindle, which has a component resisting axial movement of the first clutch member relative to the spindle. This in turn reduces the tendency of the first clutch member to move axially too rapidly relative to the spindle.
In a preferred embodiment, said second clutch member is adapted to be mounted to said first clutch member and to slide relative thereto in a direction substantially parallel to said first axis, said first and second clutch members have cooperating engaging portions, and said second biasing means is adapted to urge said cooperating engaging portions into engagement with each other, such that when a torque applied between said first and second clutch members does not exceed a predetermined value, said cooperating engaging portions engage each other to prevent relative rotation between said first and second clutch members, and when said torque exceeds said predetermined value, axial movement of said second clutch member relative to said first clutch member against the action of said second biasing means occurs to disengage said cooperating engaging portions from each other, thereby permitting relative rotation between said first and second clutch members.
The first clutch member may be adapted to abut the second clutch member, and the cooperating engaging portions may comprise a plurality of teeth on said first and second clutch members.
The teeth may be adapted to engage each other by means of cooperating inclined surfaces.
The cooperating engaging portions may comprise at least one respective third friction surface on said first clutch member and at least one fourth friction surface on said second clutch member.
The first clutch member may be a drive gear adapted to be driven by means of the motor.
The first and/or second biasing means may comprise at least one respective compression spring.
P-UK-PR1 1 16B The clutch may further comprise at least one resilient stop member adapted to engage said first clutch member at said stop.
This provides the advantage of minimising impact between the first clutch member and the stop.
Said first clutch member may further comprise a recess having an inclined surface for engaging at least one said resilient stop member.
This provides the advantage of bringing the first clutch member into more controlled engagement with the stop member.
The first clutch member may have a pair of said first friction surfaces, each said first friction surface inclined in use relative to said first axis for engaging a respective corresponding second friction surface on the spindle.
This provides the advantage of providing more effective braking of the first clutch member relative to the spindle for each direction of rotation of the spindle.
According to another aspect of the present invention, there is provided a clutch for a rotary power tool having a housing, a spindle rotatably mounted within the housing, and a motor for causing rotation of the spindle about a first axis, the clutch comprising: a first clutch member adapted to be mounted to the spindle and to rotate therewith and slide relative thereto in a direction substantially parallel to said first axis; first biasing means adapted to act between said spindle and said first clutch member for biasing said first clutch member towards a stop; a second clutch member having a first condition in which said second clutch member engages said first clutch member and rotates therewith, and a second condition in which said second clutch member can move relative to said first clutch member; second biasing means adapted to act between said first and second clutch members for urging said second clutch member towards said first condition; and at least one resilient stop member adapted to engage said first clutch member at said stop.
P-UK-PR11 1 6B By providing at least one resilient stop member adapted to engage the first clutch member at the stop, this provides the advantage of minimising impact between the first clutch member and the stop, which in turn minimises the extent to which the first clutch member is brought back into engagement with the stop on the spindle too violently.
In a preferred embodiment, said second clutch member is adapted to be mounted to said first clutch member and to slide relative thereto in a direction substantially parallel to said first axis, said first and second clutch members have cooperating engaging portions, and said second biasing means is adapted to urge said cooperating engaging portions into engagement with each other, such that when a torque applied between said first and second clutch members does not exceed a predetermined value, said cooperating engaging portions engage each other to prevent relative rotation between said first and second clutch members, and when said torque exceeds said predetermined value, axial movement of said second clutch member relative to said first clutch member against the action of said second biasing means occurs to disengage said cooperating engaging portions from each other, thereby permitting relative rotation between said first and second clutch members.
Preferably, the first clutch member is adapted to abut the second clutch member, and the cooperating engaging portions comprise a plurality of teeth on said first and second clutch members.
The teeth may be adapted to engage each other by means of cooperating inclined surfaces.
The cooperating engaging portions may comprise at least one first friction surface on said first clutch member and a respective second friction surface on said second clutch member.
Said first clutch member may further comprise a recess having an inclined surface for engaging at least one said resilient stop member.
This provides the advantage of bringing the first clutch member into more controlled engagement with the stop member.
P-UK-PR11 1 6B Said first clutch member may further comprise at least one third friction surface inclined in use relative to said first axis for engaging a respective corresponding fourth friction surface on said spindle.
By providing a first clutch member having at least one third friction surface inclined relative to the first axis for engaging a respective corresponding fourth friction surface on the spindle, this provides the advantage of providing a reaction force, from the or each corresponding fourth friction surface on the spindle, which has a component resisting axial movement of the first clutch member relative to the spindle. This in turn reduces the tendency of the first clutch member to move axially too rapidly relative to the spindle.
The first clutch member may have a pair of said third friction surfaces, each said third friction surface inclined in use relative to said first axis for engaging a respective corresponding fourth friction surface on the spindle.
This provides the advantage of providing more effective braking of the first clutch member relative to the spindle for each direction of rotation of the spindle.
The first clutch member may be a drive gear adapted to be driven by means of the motor.
The first and/or second biasing means may comprise at least one respective compression spring.
According to a further aspect of the present invention, there is provided a rotary power tool comprising: a housing; a spindle rotatably mounted within the housing; a motor for causing rotation of said spindle about an axis; and a clutch as defined above mounted to said spindle.
Said cooperating engaging portions may comprise a tapered projection on one of said first and second clutch member and a tapered groove on the other of said first and second clutch members.
P-UK-PR11 1 6B The tool may be a hammer.
A preferred embodiment of the invention will now be described, by way of example only, and not in any limitative sense, with reference to the accompanying drawings, in which: Figure 1 is a partially cut-away side cross-sectional elevation view of a rotary hammer embodying the present invention; Figure 2 is a partially cut away perspective view of a spindle and overload clutch mechanism of the hammer of Figure 1; Figure 3 is a rear end view of the mechanism of Figure 2; Figure 4 is a sectional view along the line A-A in Figure 3; Figure 5 is a sectional view along the line B-B in Figure 3; Figure 6 is a sectional view along the line C-C in Figure 3; Figure 7 is a sectional view along the line O-D in Figure 4; Figure 8 is a perspective view of the spindle shown in Figure 2 with the overload clutch mechanism removed; and Figure 9 is a cross-sectional elevation view of the rotary hub shown in Figure 2.
Referring to Figure 1, a rotary hammer has a forward portion shown in cross section, and a rear portion incorporating a motor and pistol grip rear handle in a conventional manner. Alternatively, the handle may be of the D handle type. The handle portion incorporates a trigger switch 7 for actuating an electric motor which carries a pinion (not shown) at the forward end of its armature shaft. The pinion of the motor rotatingly drives an intermediate shaft 6 via a gear which is press fit onto the rearward end of the intermediate shaft 6. The intermediate shaft 6 is rotatably mounted in a housing 2 of the hammer via a first bearing (not shown) located at the rearward end of the intermediate shaft 6 and a forward bearing 3 located at the forward end of the intermediate shaft 6.
A wobble drive hammering mechanism, of a type which will be familiar to persons skilled in the art, is provided for reciprocatingly driving a piston 24. The piston 24 is slidably located within a hollow cylindrical spindle 4 and an O-ring seal (not shown) is mounted around the piston 24 so as to seal between the periphery of the piston 24 and the internal surface of the spindle 4. A ram 28 is slidably mounted within the spindle 4 and an O-ring seal (not shown) is mounted around the ram 28 so as to seal between P-UK-PR11 1 6B the periphery of the ram 28 and the internal surface of the spindle 4. In this way, during normal operation of the hammer, a closed air cushion is formed between the forward face of the piston 24 and the rear face of the ram 28, which causes the ram to be reciprocatingly driven by the piston via the closed air cushion. During normal operation of the hammer, the ram 28 repeatedly impacts a beatpiece 32, which is reciprocatingly mounted within the spindle 4. The beatpiece 32 transfers impacts from the ram 28 to a tool or bit (not shown) mounted within a forward tool holder portion of the spindle 4 by means of a tool holder arrangement 36, of a type which will be familiar to persons skilled in the art. The tool or bit is releasably locked within the tool holder portion of the spindle 4 so as to be able to reciprocate within the tool holder portion of the spindle by a limited amount.
The spindle 4 is rotatably mounted in the hammer housing 2 by means of bearings 5, 7. Simultaneously with, or as an alternative to, the hammering action generated by the hammering mechanism described above, the spindle 4 can be rotatingly driven by the intermediate shaft 6 as described below. Thus, as well as reciprocating, the tool or bit is rotatingly driven because it is non-rotatably mounted within the spindle 4 by the tool holder arrangement 36.
An overload clutch mechanism includes a spindle drive gear 40 rotatably and axially slidably mounted on a slider sleeve 41, and the slider sleeve 41 is non-rotatably and axially slidably mounted on the spindle 4. The spindle drive gear 40 is formed on its periphery with a set of teeth 43. The intermediate shaft 6 is formed at its forward end with a pinion 38 and the teeth 43 of the spindle drive gear 40 may be brought into engagement with the pinion 38 in order to transmit rotary drive to the slider sleeve 41 and thereby to the spindle 4. The spindle drive gear 40 transmits rotary drive to the slider sleeve 41 via the overload clutch arrangement. The spindle drive gear 40 has a set of rearwardly facing teeth 40a formed on a rearward facing surface thereof, this set of teeth 40a being biased into engagement with a set of teeth formed on a forward facing surface 41a on an annular flange of the slider sleeve 41. The sets of teeth are biased into engagement with each other by a spring 47 mounted on the slider sleeve 41 to extend between a washer 49 axially fixedly mounted at the forward end of the slider sleeve 41, and a forward facing end surface of the spindle drive gear 40.
The slider sleeve 41 is axially biased by means of a spring 56 into a rearward position against an elastomeric O-ring 42 mounted in a recess 102 (Figures 4 and 5) P-UK-PR11 1 6B formed in the external surface of the spindle 4 and having an inclined surface. In the rearward position, the hammer is in a rotary mode and rotation of the intermediate shaft 6 is transmitted to the spindle 4, provided the torque transmitted is below a threshold torque of the overload clutch, the operation of which will be described in greater detail below.
The slider sleeve 41 can also be moved into a forward position against the biasing force of the spring 56 via a mode change mechanism. In the forward position, the spindle drive gear 40 is moved on the slider sleeve 41 forwardly out of engagement with the intermediate shaft pinion 38 and into engagement with a spindle lock arrangement 60, the function of which is not relevant to the present invention and will therefore not be described in further detail. With the slider sleeve 41 and spindle drive gear 40 in a forward position, the hammer is in a non-rotary mode with the spindle 4 fixed against rotation. The mode change arrangement may comprise a mode change knob 55 rotatably mounted on the housing 2 and having an eccentric pin 57 which is engageable with the rearward face of the annular flange 41a of the slider sleeve 41 to move the slider sleeve forwardly.
In the position shown in Figure 1, the spring 56 biases the slider sleeve 41 into its rearward position. However, on rotation of the mode change knob through 180 degrees from its position shown in Figure 1, the eccentric pin 57 pulls the slider sleeve 41 forwardly against the biasing force of the spring 56. The eccentric pin 57 then pulls the slider sleeve 41 forwardly to move the spindle drive gear 40 out of engagement with the pinion 38 of the intermediate shaft 6 and into engagement with the spindle lock arrangement 60.
Referring now to Figures 2 and 8, the external surface of the spindle 4 is formed with a series of tapering grooves 104 which become narrower in a direction moving towards the forward end of the spindle 4. The slider sleeve 41 is provided with splines 106 which also taper in a direction towards the forward end of the slider sleeve 41. In this way, the slider sleeve 41 is prevented from rotating relative to the spindle 4, but can slide axially to a limited extent relative thereto. Referring to Figures 4 and 5, the rearward end of the slider sleeve 41 is provided with a recess 108 having an inclined internal surface for accommodating elastomeric O-ring 42.
The operation of the rotary hammer will now be described.
P-UK-PR11 1 6B When the torque required to rotationally drive the spindle 4 is below a predetermined threshold, the spring 56 biases the slider sleeve 41 into engagement with elastomeric O-ring 42, and the spring 47 biases the sets of cooperating teeth on the spindle drive gear 40 and slider sleeve 41 into engagement with each other. With these sets of cooperating teeth engaged, rotation of the intermediate shaft 6 rotationally drives the spindle drive gear 40 via pinion 38, and the spindle drive gear 40 rotationally drives the slider sleeve 41 via the interlocking facing teeth. As a result, the slider sleeve 41 rotationally drives the spindle 4 by means of cooperation between the splines 106 on the slider sleeve 41 and the grooves 104 on the sleeve 4.
When the torque required to rotationally drive the spindle 4 exceeds the predetermined torque threshold, however, the inclined surfaces of the mutually engaging teeth on the spindle drive gear 40 and slider sleeve 41 slide over each other, as a result of which the drive gear 40 slides forwardly along the slider sleeve 41 against the action of spring 47. This may occur, for example, as a consequence of the hammer bit becoming stuck in a hard workplace such as concrete. As a result, the spindle drive gear 40 can rotate relative to the slider sleeve 41 and the cooperating sets of teeth ratchet over each other, preventing the rotary drive from the spindle drive gear 40 being transmitted to the spindle 4. Furthermore, the ratcheting of the sets of teeth makes a noise which alerts the user of the hammer to the fact that the overload clutch arrangement is slipping.
In the event of a very rapid increase in the torque applied to the clutch, for example as a result of the hammer bit (not shown) becoming stuck in a workpiece such as concrete, the slider sleeve 41 may also be moved forward rapidly against the action of spring 56, and one of the side surfaces of each spline 106 comes into contact with the facing surface of the groove 104 in the spindle 4. As a result, the splines and grooves abut each other at a sliding surface angled relative to the axis of rotation of the spindle 4, which abutment between the splines 106 and grooves 104 produces a reaction force having a component parallel to the axis of rotation of the spindle 4, tending to slow down movement of the slider sleeve 41 relative to the spindle 4. It has been found that this significantly reduces problems caused by rapid forward movement of the slider sleeve 41 relative to the sleeve.
35As the slider sleeve 41 is urged backwards towards O-ring 42 under the action of spring 56, as the inclined surface of recess 108 in the rear face of slider sleeve 41 P-UK-PR11 1 6B comes into contact with the Oring 42, and the slider sleeve 41 returns to its rest position more uniformly and with less impact than in the case of a solid ring such as a circlip replacing the O-ring 42.
It will be appreciated by persons skilled in the art that the above embodiment has been described by way of example only and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims. For example, although the embodiment described in detail above is a torque overload clutch, it will be appreciated by persons skilled in the art that clutches of a different type may also be within the scope of the present invention.
P-UK-PR1 1 16B

Claims (24)

1. A clutch for a rotary power tool having a housing, a spindle rotatably mounted within the housing, and a motor for causing rotation of said spindle about a first axis, the clutch comprising: a first clutch member adapted to be mounted to said spindle and to rotate therewith and slide relative thereto in a direction substantially parallel to said first axis, said first clutch member having at least one first friction surface inclined in use relative to said first axis for engaging a respective corresponding second friction surface on said spindle as a result of movement of said first clutch member relative to the spindle; first biasing means adapted to act between said spindle and said first clutch member for biasing said first clutch member towards a stop; a second clutch member having a first condition in which said second clutch member engages said first clutch member and rotates therewith, and a second condition in which said second clutch member can move relative to said first clutch member; and second biasing means adapted to act between said first and second clutch members for urging said second clutch member towards said first condition.
2. A clutch according to claim 1, wherein said second clutch member is adapted to be mounted to said first clutch member and to slide relative thereto in a direction substantially parallel to said first axis, said first and second clutch members have cooperating engaging portions, and said second biasing means is adapted to urge said cooperating engaging portions into engagement with each other, such that when a torque applied between said first and second clutch members does not exceed a predetermined value, said cooperating engaging portions engage each other to prevent relative rotation between said first and second clutch members, and when said torque exceeds said predetermined value, axial movement of said second clutch member relative to said first clutch member against the action of said second biasing means occurs to disengage said cooperating engaging portions from each other, thereby permitting relative rotation between said first and second clutch members.
3. A clutch according to claim 2, wherein the first clutch member is adapted to abut the second clutch member, and the cooperating engaging portions comprise a plurality of teeth on said first and second clutch members.
P-UK-PR11 1 6B
4. A clutch according to claim 3, wherein the teeth are adapted to engage each other by means of cooperating inclined surfaces.
5. A clutch according to any one of claims 2 to 4, wherein the cooperating engaging portions may comprise at least one third friction surface on said first clutch member and at least one fourth friction surface on said second clutch member.
6. A clutch according to any one of the preceding claims, wherein the first clutch member is a drive gear adapted to be driven by means of the motor.
7. A clutch according to any one of the preceding claims, wherein the first and/or second biasing means comprise at least one respective compression spring.
8. A clutch according to any one of the preceding claims, further comprising at least one resilient stop member adapted to engage said first clutch member at said stop.
9. A clutch according to claim 8, wherein said first clutch member further comprises a recess having an inclined surface for engaging at least one said resilient stop member.
10. A clutch according to any one of the preceding claims, wherein the first clutch member has a pair of said first friction surfaces, each said first friction surface inclined in use relative to said first axis for engaging a respective corresponding second friction surface on the spindle.
11. A clutch for a rotary power tool having a housing, a spindle rotatably mounted within the housing, and a motor for causing rotation of the spindle about a first axis, the clutch comprising: a first clutch member adapted to be mounted to the spindle and to rotate therewith and slide relative thereto in a direction substantially parallel to said first axis; first biasing means adapted to act between said spindle and said first clutch member for biasing said first clutch member towards a stop; a second clutch member having a first condition in which said second clutch member engages said first clutch member and rotates therewith, and a second condition in which said second clutch member can move relative to said first clutch member; P-UK-PR11 1 6B 4i second biasing means adapted to act between said first and second clutch members for urging said second clutch member towards said first condition; and at least one resilient stop member adapted to engage said first clutch member at said stop.
12. A clutch according to claim 11, wherein said second clutch member is adapted to be mounted to said first clutch member and to slide relative thereto in a direction substantially parallel to said first axis, said first and second clutch members have cooperating engaging portions, and said second biasing means is adapted to urge said cooperating engaging portions into engagement with each other, such that when a torque applied between said first and second clutch members does not exceed a predetermined value, said cooperating engaging portions engage each other to prevent relative rotation between said first and second clutch members, and when said torque exceeds said predetermined value, axial movement of said second clutch member relative to said first clutch member against the action of said second biasing means occurs to disengage said cooperating engaging portions from each other, thereby permitting relative rotation between said first and second clutch members.
13. A clutch according to claim 12, wherein the first clutch member is adapted to abut the second clutch member, and the cooperating engaging portions comprise a plurality of teeth on said first and second clutch members.
14. A clutch according to claim 13, wherein the teeth are adapted to engage each other by means of cooperating inclined surfaces.
15. A clutch according to any one of claims 12 to 14, wherein the cooperating engaging portions comprise at least one first friction surface on said first clutch member and a respective second friction surface on said second clutch member.
16. A clutch according to any one of claims 1 1 to 15, wherein said first clutch member further comprises a recess having an inclined surface for engaging at least one said resilient stop member.
17. A clutch according to any one of claims 11 to 16, wherein said first clutch member further comprises at least one third friction surface inclined in use relative to said first axis for engaging a respective corresponding fourth friction surface on said spindle.
P-UK-PR11 1 6B
18. A clutch according to claim 17, wherein the first clutch member has a pair of said third friction surfaces, each said third friction surface inclined in use relative to said first axis for engaging a respective corresponding fourth friction surface on the spindle.
19. A clutch according to any one of claims 11 to 18, wherein the first clutch member is a drive gear adapted to be driven by means of the motor.
20. A clutch according to any one of claims 11 to 19, wherein the first and/or second biasing means comprise at least one respective compression spring.
21. A clutch for a rotary power tool having a housing, a spindle rotatably mounted within the housing, and a motor for causing rotation of said spindle about a first axis, the clutch substantially as hereinbefore described with reference to the accompanying drawings.
22. A rotary power tool comprising: a housing; a spindle rotatably mounted within the housing; a motor for causing rotation of said spindle about an axis; and a clutch according to any one of the preceding claims mounted to said spindle.
23. A tool according to claim 22 and any one of claims 2 to 5 or 12 to 16, wherein said cooperating engaging portions comprise a tapered projection on one of said first and second clutch member and a tapered groove on the other of said first and second clutch members.
24. A tool according to claim 22 or 23, wherein the tool is a hammer.
P-UK-PR11 1 6B
GB0325879A 2003-04-17 2003-11-06 Slip clutch for rotary power tool Withdrawn GB2407851A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
GB0325879A GB2407851A (en) 2003-11-06 2003-11-06 Slip clutch for rotary power tool
EP04008739A EP1468789A3 (en) 2003-04-17 2004-04-13 Clutch for rotary power tool and rotary power tool incorporating such clutch
US10/825,838 US7216749B2 (en) 2003-04-17 2004-04-16 Clutch for rotary power tool and rotary power tool incorporating such clutch

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB0325879A GB2407851A (en) 2003-11-06 2003-11-06 Slip clutch for rotary power tool

Publications (2)

Publication Number Publication Date
GB0325879D0 GB0325879D0 (en) 2003-12-10
GB2407851A true GB2407851A (en) 2005-05-11

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ID=29726018

Family Applications (1)

Application Number Title Priority Date Filing Date
GB0325879A Withdrawn GB2407851A (en) 2003-04-17 2003-11-06 Slip clutch for rotary power tool

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Country Link
GB (1) GB2407851A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2411702A (en) * 2004-02-27 2005-09-07 Nifco Inc Clutch with a brake disconnect device.

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3866692A (en) * 1973-02-02 1975-02-18 Rockwell International Corp Power tools
GB1518675A (en) * 1974-10-14 1978-07-19 Braune R Mechanical rotary couplings
GB2327988A (en) * 1997-08-01 1999-02-10 British Autogard Torque limiting clutch with supplementary biasing means or manual disengagement

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3866692A (en) * 1973-02-02 1975-02-18 Rockwell International Corp Power tools
GB1518675A (en) * 1974-10-14 1978-07-19 Braune R Mechanical rotary couplings
GB2327988A (en) * 1997-08-01 1999-02-10 British Autogard Torque limiting clutch with supplementary biasing means or manual disengagement

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
US 2002003044 A *
US 2003146007 A *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2411702A (en) * 2004-02-27 2005-09-07 Nifco Inc Clutch with a brake disconnect device.
US7188718B2 (en) 2004-02-27 2007-03-13 Nifco Inc. Clutch device for transmitting drive power to transmission receiving member
GB2411702B (en) * 2004-02-27 2007-10-03 Nifco Inc Clutch device for transmitting drive power to transmission receiving member

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