Abstract:
A power tool, for example a hammer drill comprising: a housing; a handle having two ends, the first end being moveably mounted to the housing via a first mounting assembly, the second end being moveably mounted to the housing via a second mounting assembly; wherein the first mounting assembly comprises: a first part mounted on the housing and a second part mounted on the first end of the handle, one part comprising a sleeve, the other part comprising a rod mounted in an axially slideable manner in the sleeve to enable the first end of the handle to slide towards or away from the housing; and a biasing mechanism connected between the two parts which biases the first end of the handle away from the housing; wherein the second mounting assembly comprises: a third part mounted on the body and a fourth part mounted on the second end of the handle, one part comprising a support, the other part comprising a pin located in the support which is capable of being rotated in the support to enable the second end of the handle to rotate relative to the housing and to move linearly in the support to enable the second end of the handle to move linearly relative to the housing; characterized in that the support comprises a passage in which the pin is located, the pin being capable of freely moving within the passage either rotationally to enable the second end of the handle to rotate relative to the housing or linearly to enable the second end of the handle to move linearly relative to the housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority, under 35 U.S.C. §119(a)-(d), to UK Patent Application No. GB 10 131 75.3 filed Aug. 5, 2010, the contents of which is incorporated herein by reference in its entirety. The disclosure of GB 2456805 which was filed on Jul. 29, 2009 is also incorporated herein by reference in its entirety. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to a handle for a power tool, in particular for a hammer drill, and in particular, to a mounting assembly for a rear handle on a hammer drill which reduces the amount of vibration transmitted to the handle. 
       BACKGROUND OF THE INVENTION 
       [0003]    Power tools of all types comprise a body attached to which are handles by which an operator can support the tool. Vibrations are generated in the body during the operation of such tools which are transferred to the handles. It is desirable to minimize the amount of transfer. 
         [0004]    A hammer drill can operate in one or more of the following modes of operation; hammer only mode, drill only mode and combined hammer and drill mode. EP1157788 discloses such a hammer. During the operation of such hammers, a considerable amount of vibration can be generated. The vibration is caused by the operation of the rotary drive mechanisms and/or the hammer mechanisms, depending on the mode of operation of the hammer drill, combined with the vibratory forces applied to and experienced by the cutting tool, such as a drill bit or chisel when it is being used on a work piece. These vibrations are transferred to the body of the hammer drill, which in turn are transferred to a rear handle being used by the operator to support the hammer drill. The transfer of vibration to the rear handle from the body, and subsequently to the operator&#39;s hand can not only be painful but can result in injury, particularly when the hammer drill is used over long periods of time. It is therefore desirable to minimise the amount of vibration transferred from the body to the rear handle. 
         [0005]    One solution is to moveably mount the rear handle on the body of the hammer drill to allow relative movement between the two and to locate a vibration dampening mechanism between the body and the rear handle to minimise the amount of vibration transferred to the rear handle from the body. 
         [0006]    GB2456805 describes such a vibration dampening mechanism for a hammer drill with reference to FIGS. 22 to 32 by which the amount of vibration transferred to the rear handle from the body is reduced. The rear handle 294 (using the same reference numbers as GB2456805) is connected via an upper mounting assembly 308, which enables the upper part of the handle 294 to slide relative to the upper part of the housing 290, and a lower mounting assembly 310, which enables a pivoting movement of the lower part of the handle relative to the lower part of the housing. Both the upper mounting assembly 308 and the lower mounting assembly 310 comprise vibration dampening mechanisms which reduce the amount of vibration transferred to the rear handle 294 from the housing 290. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    Accordingly there is provided a power tool comprising: 
         [0008]    a housing; 
         [0009]    a handle having two ends, the first end being moveably mounted to the housing via a first mounting assembly, the second end being moveably mounted to the housing via a second mounting assembly; 
         [0010]    wherein the first mounting assembly comprises: 
         [0011]    a first part mounted on the housing and a second part mounted on the first end of the handle, one part comprising a sleeve, the other part comprising a rod mounted in an axially slideable manner in the sleeve to enable the first end of the handle to slide towards or away from the housing; and 
         [0012]    a biasing mechanism connected between the two parts which biases the first end of the handle away from the housing; 
         [0013]    wherein the second mounting assembly comprises: 
         [0014]    a third part mounted on the body and a fourth part mounted on the second end of the handle, one part comprising a support, the other part comprising a pin located in the support which is capable of being rotated in the support to enable the second end of the handle to rotate relative to the housing and to move linearly in the support to enable the second end of the handle to move linearly relative to the housing; 
         [0015]    characterized in that the support comprises a passage in which the pin is located, the pin being capable of freely moving within the passage either rotationally to enable the second end of the handle to rotate relative to the housing or linearly to enable the second end of the handle to move linearly relative to the housing. 
         [0016]    Preferably the power tool is a hammer drill and the handle is a rear handle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    Two embodiments of the present invention will now be described with reference to drawings of which: 
           [0018]      FIG. 1  shows a sketch of a side view of a hammer drill; 
           [0019]      FIG. 2  shows a vertical cross sectional view of the rear handle of the first embodiment of the present invention; 
           [0020]      FIG. 3  shows a vertical cross sectional view of the lower section of the rear handle in the directions of Arrows A in  FIG. 2 ; 
           [0021]      FIG. 4  shows a vertical cross sectional view of the lower section of the rear handle in the directions of Arrows B in  FIG. 3 ; 
           [0022]      FIG. 5A  shows a side view of the insert and  FIG. 5B  shows a cross section view of the insert in the direction of Arrow M in  FIG. 5A ; 
           [0023]      FIG. 6  shows a horizontal part cross sectional view of the rod and sleeve of the upper mounting assembly in the directions of Arrows C in  FIG. 2 ; 
           [0024]      FIG. 7  shows a vertical cross sectional view of the rear handle of the second embodiment of the present invention; and 
           [0025]      FIG. 8  shows a side view of the insert according to the second embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0026]    Referring to  FIG. 1 , a hammer drill comprises a main housing  2  which comprises a motor housing  4 , in which is mounted an electric motor  6 , a gear housing  8  in which is mounted a rotary drive and hammer mechanism  10 , and a rear housing  12 . The motor housing  4  is connected to the gear housing using bolts  20 . Similarly, the rear housing  12  is attached to both of the motor housing  4  and gear housing  8  using bolts  22 . A tool holder  14  is mounted on the front of the gear housing  8  which is capable of holding a cutting tool  16 , such as a drill bit. The motor  6  rotatingly and/or reciprocatingly drives the cutting tool  16  via the rotary drive and/or hammer mechanism  10 . The hammer drill can operate in three modes of operation, namely hammer only mode, drill only mode and combined hammer and drill mode. A mode change knob  18  is rotatably mounted on the top of the gear housing  8 . Rotation of the knob  18  to predetermined angular positions activates or deactivates the rotary drive and/or hammer mechanism  10  to adjust the mode of operation of the hammer drill. 
         [0027]    A rear handle  24  is moveably mounted to the rear housing  12  as will be described in more detail below. The rear handle  24  is manufactured from a plastic clam shell which provides a hollow cavity inside of the handle in which component parts of the hammer can located. A trigger switch  26  is mounted on the rear handle  24 . An electric cable  28  enters the base of the rear handle  24  and connects to the electric motor via the trigger switch  26 . Depression of the trigger switch  26  activates the motor. A rubber soft grip  50  is moulded onto the rear of the rear handle  24  in well known manner. 
         [0028]    The first embodiment of the present invention will now be described with reference to  FIGS. 2 to 6 . 
         [0029]    The rear handle is mounted to the rear housing  12  at its two ends  30 ,  32 . The top end  30  is mounted to the rear housing  12  via an upper mounting assembly  34 . The upper mounting assembly  34  allows the top end  30  of the handle  12  to move towards or away from (Arrow D) the rear housing  12  over a large range of movement, whilst allowing limited movement in the directions of Arrows E and F relative to rear housing  12 . The lower end  32  is mounted to the rear housing  12  via a lower mounting assembly  36 . The lower mounting assembly  36  allows the lower end  32  of the handle to pivot (Arrow G—see  FIG. 4 ) about a horizontal axis  58  relative to the rear housing  12 , whilst allowing limited linear movement in the directions of Arrows D and E. 
         [0030]    The upper mounting assembly  34  will now be described with reference to  FIGS. 2 and 6 . The upper mounting assembly  34  comprises a metal rod  38  which is rigidly attached to the rear housing  12  using a bolt  40 . The bolt  40  passes through a hole  46  in the rear housing  12  and through the length of the rod  38 . The head  42  of the bolt  40  abuts the rear housing  12 . A nut  44  is screwed on the end of the bolt  40  and sandwiches the rod  38  and the part of the rear housing  12  with the aperture  46  between the head  42  of the bolt and the nut  44  thus locking the rod  38  to the rear housing  12 . 
         [0031]    The free end of the rod  38  comprises a rectangular portion  52 , the height (vertically) of which is the same as the rod  38  (as seen in  FIG. 2 ), but the width (horizontally) of which is greater than the rod  38  (see  FIG. 6 ). 
         [0032]    Rigidly mounted inside the cavity at the top end  30  of the rear handle  24  is a plastic tubular sleeve  54 . The shaft of the rod  38  passes through the length of the tubular aperture  56  formed by the sleeve  54 . The length of the shaft of the rod  38  is greater than the length of the sleeve  54 . The dimensions of the cross section area of the tubular aperture  36  of the sleeve are slightly greater than the dimensions of the cross section area of the rod  38  so that a small gap is formed between the outer surface of the shaft of the rod  38  and the inner wall of the tubular aperture  56 . The rectangular portion  52  of the rod  38  locates at one end of the sleeve  54 . The width of the rectangular end of the rod  38  is greater than the width of the tubular aperture  56  and the sleeve  54  (see  FIG. 6 ). As such, it is too wide for it to pass through the tubular aperture  56 . The other end of the rod  38  which is attached to the rear housing is located at the other end of the sleeve and is prevented from entering the tubular aperture  56  by the rear housing  12 . The rod  38  can freely slide in an axial direction (Arrow D) within the sleeve  54 , the range of axial movement being limited at one end of the range by the rear housing  12  engaging with one end of the sleeve  54  and at the other end of the range by the rectangular portion  52  engaging with the other end of the sleeve  54 . As the dimensions of the cross section area of the tubular aperture  36  of the sleeve are slightly greater than the dimensions of the cross section area of the rod  38  to produce a small gap between the outer surface of the shaft of the rod  38  and the inner wall of the tubular aperture  56 , limited movement of the rod  38  inside of the sleeve is allowed in the directions of Arrows E and F relative to rear housing  12 . 
         [0033]    Connected between the rear housing  12  and top end  30  of the rear handle  24  is a helical spring  60  which surrounds the rod  38 . The spring biases the top end  30  of the rear handle  24  away from the rear housing  12 . When the spring  60  biases the top end of the rear handle away by the maximum amount, the rectangular portion  52  engages with the end of the sleeve  54 , preventing further movement of the top end  30  of the handle  24  away from the rear housing  12 . The spring  60  is under a small compression force in this state. When the top end  30  of the rear handle is moved towards the rear housing  12  against the biasing force of the spring  60  by the application of an external force, the spring  60  becomes further compressed and shortens in length as the rod  38  axially slides within the sleeve  54  until the rear housing engages with the other end of the sleeve  54 . When the external force is removed, the top end  30  of the rear handle  24  moves away from the rear housing due to the biasing force of the spring  60 , the rod  38  axially sliding within the sleeve  54  until the rectangular portion  52  engages the end of the sleeve  54 . The spring  60  also applies a biasing force on the rod  38  in a direction of Arrows E and F, urging the rod  38  to a central position within the sleeve  54 . As such, when no external forces are applied to the rear handle  24 , the spring  60  also locates the rod  38  centrally within the tubular aperture  56  so that a gap is formed around the whole of the outer surface of the rod and the inner wall of the sleeve  54 . Movement of the rod in directions of Arrows E or F causes the rod  38  to move towards an inner wall of the tubular aperture  56  against a side way biasing force generated by the spring  60 . 
         [0034]    A set of bellows  62  connects between the rear housing  12  and the top  30  of the handle and surrounds the rod  38  and spring  60 . 
         [0035]    The lower mounting assembly  36  will now be described with reference to  FIGS. 2 to 5 . 
         [0036]    The lower mounting assembly  34  comprises a metal pin  70  of circular cross section which is mounted inside the lower end  32  of the handle. The pin  70  has a longitudinal axis  58 . The pin  70  extends side ways (generally in the direction of Arrow F) relative to the handle  24 . The pin  70  is rigidly connected to the side walls  72  of the lower end  32  of the handle  24  and traverses the cavity inside of the handle  24 . 
         [0037]    The rear housing  12  comprises a projection  74  which extends rearwardly and projects into the cavity of the handle  24  at the lower end of the handle  24  in the vicinity of the pin  70 . Formed through projection is a hollow passage  76 . The hollow passage  76  similarly extends side ways (in the direction of Arrow F). The pin  70  passes through the length of the hollow passage  76 , each end of the pin  70  extending beyond an end of the hollow passage  76  and connecting to the side wall  72  of the handle  24 . The cross sectional area of the hollow passage  76  is greater than the cross sectional area of the pin  70 , allowing the pin  70  to move sideways (in the direction of Arrows D and E) inside of the passageway  76 , as well as being able to feely pivot (in the direction of Arrow G) within the hollow passage  76 . 
         [0038]    Located inside each end of the hollow passage  76  is an insert  78 . Each insert  78  is of identical size and is rigidly connected to the inner wall of the hollow passage  76  to prevent movement of the insert  78  relative to the projection  74 . An aperture  80 , with an oval cross section, is formed through each insert  78  (see  FIGS. 5A and 5B ) and which extends in the same direction as the hollow passage  76 . The pin  70  passes through each of the apertures  80 . The two apertures  80  are aligned with each other inside of the projection  74 . 
         [0039]    The width  82  of the aperture  80  is marginally greater that the diameter of the pin  70 . The length  84  of the aperture is twice the size of the diameter of the pin  70 . As such, the pin can side sideways in a lengthwise direction  84  in the aperture  80 . 
         [0040]    The pin  70  is prevented from sliding sideways  88  through the aperture  80  by the side walls  72  of the lower end  32  of the handle  24 , to which the pin  70  is rigidly attached, abutting directly against the sides of the inserts  78 . 
         [0041]    The hammer drill (excluding the rear handle  24 ) has a centre of gravity  86 . A centre of gravity axis  120  passes through the centre of gravity. The centre of gravity axis is horizontal and extends width ways in the direction of Arrow F. The inserts are mounted in side the hollow passage  76  with aperture  80  orientated so that the lengthwise direction  84  of the aperture  80  extends tangentially to a circle (with radius R) centered on the centre of gravity axis  120  of the hammer drill (see  FIG. 1 ) in a plane which extends in the directions of Arrows D and E (It should be noted that a plane which extends in the directions of Arrows D and E is a lengthwise vertical plane. A plane which extends in the directions of Arrows F and E is width way vertical plane). 
         [0042]    When no force is applied to the rear handle  24  by an operator, the pin  70  is biased to the centre, in the lengthwise direction  84 , of the aperture  80  of each insert  80 , with equal space within the aperture  80  being left on either side of the pin  70  in the lengthwise direction  84 . The biasing force acting on the pin  70  is generated by the spring  60  in the upper mounting assembly  34  which urges the pin  70  to the central position. Sliding movement of the pin  70  in the aperture, in the lengthwise direction  84 , towards either of the ends of the oval aperture, is against the biasing force of the spring  60 . 
         [0043]    A set of bellows  90  connects between the rear housing  12  and the lower end  32  of the handle  24 . 
         [0044]    During use, the operator supports the hammer drill using the rear handle  24 . When the operator places the cutting tool against a work piece, the operator applies a pressure to the rear handle  24 , causing the rear handle  24  to move towards the rear housing  12  of the hammer. The top end  30  moves towards the rear housing  12  by the rod  38  axially sliding within the sleeve  54  against the biasing force of the spring  60 , reducing the length of the spring  60  as it becomes compressed. The lower end  32  pivots about the pin  70 . Depression of the trigger  26  activates the motor  6  which drives the cutting tool  16 . 
         [0045]    During the operation of the hammer, vibrations are generated by the operation of the motor  6  and the rotary drive and hammer mechanism  10 . These vibrations are transferred to the rear housing  12 . Significant vibrations are generated in two directions in particular. The first direction is in a linear direction (Arrow D) parallel to a longitudinal axis  92  of the cutting tool  16 . The second direction is in a circular direction (Arrow H) about the centre of gravity axis  120  of the hammer. This is caused by the centre of gravity  86  being located away from the longitudinal axis  92  of the cutting tool  16 , in this case, below the longitudinal axis  92 . 
         [0046]    Vibrations in the first direction are mainly absorbed by the upper mounting assembly  134 , and by the spring  60  in particular. As the rear housing  12  vibrates in the first direction, the rod  38  can axially slide in and out of the sleeve  54  under the influence of the vibrations, the spring  60  expanding and compressing as it does so. The dampening action of the spring  60  results in a reduction in the amount of vibration transferred to the rear handle  24  from the rear housing  12 . As the rod  38  axially slides in and out of the sleeve  54  under the influence of the vibrations, the rear handle  12  pivots about the pin  70  in the lower mounting assembly  36  as it engages with the side walls of the oval aperture  80  as the pin  70  is urged by the vibrations in the first direction to move in a direction parallel to the longitudinal axis  92  of the cutting tool  16 . 
         [0047]    If the operator applies more pressure to the rear handle  24 , the spring  60  becomes more compressed, thus transferring the additional force to the rear housing  12  of the hammer drill. However, its compression and expansion due to the vibration continues to result in a reduction of vibration being transferred to the rear handle  24  from the rear housing  12 . 
         [0048]    Vibrations in the second direction result in a twisting movement of the housing  2 , motor  6  and the rotary drive and hammer mechanism  10  about the centre of gravity axis  120  (Arrow H). These vibrations are mainly absorbed by the lower mounting assembly  36 . As the pin  70  is located in the oval slot  80  of the insert  78  which is orientated so that the lengthwise direction  84  of the aperture  80  extends tangentially to a circle centered on the centre of gravity axis  120  which extends in a lengthwise vertical plane, the pin  70  can slide tangentially relative to the centre of gravity axis  120 , allowing housing  2 , motor  6  and the rotary drive and hammer mechanism  10  to twist about the centre of gravity axis  120  relative to the rear handle  24 . This twisting movement is then damped due to the action of the spring  60  in the upper mounting mechanism  32  which biases the pin  70  to the centre of the oval slot  80 . The twisting movement of the housing  2 , motor  6  and the rotary drive and hammer mechanism  10  about the centre of gravity axis  120  relative to the rear handle  24  is accommodated by the top mounting assembly  34  by the gap formed between the outer surface of the rod  38  and the inner wall of the sleeve  54 . As the rod  38  being urged to a central position within the sleeve  54  by the spring  60 , when vibrations in the second direction are applied, the rod  38  can move sideways (Arrow E) within the sleeve  54 . The spring  60 , which biases the rod  38  centrally within the tubular aperture  36 , also dampens the movement of the rod  38  in the sleeve  54 . 
         [0049]    A second embodiment of the invention will now be described with reference to  FIGS. 7 and 8 . Where the same features shown in the second embodiment are present in the first embodiment, the same reference numbers have been used. 
         [0050]    The upper mounting assembly  34  in the second embodiment is the same as the upper mounting assembly in the first embodiment. The lower mounting assembly  36  in the second embodiment is the same as the lower mounting assembly in the first embodiment except for the shape of the cross section of the aperture  80 ′ through the insert  78 . Everything else is the same. 
         [0051]    The shape of the cross section of the aperture  80 ′ is semi-circular. The cross section has a flat wall  100  and a circular curved wall  192 . The radius  104  of the curved wall  102  is twice the diameter of the pin  70  which passes through it. 
         [0052]    The hammer drill (excluding the rear handle  24 ) has a centre of gravity  86  with a horizontal width ways centre of gravity axis  120  passing through it. The inserts  78  with the semi-circular apertures  80 ′ are mounted in side the hollow passage  76  with aperture  80 ′ orientated so that the flat wall  100  of the aperture  80 ′ extends (Arrows N) tangentially to a circle (with radius R) centered on the centre of gravity axis  120  of the hammer drill in a lengthwise vertical plane in the directions of Arrows D and E (see  FIG. 8  which shows a schematic diagram). 
         [0053]    When no force is applied to the rear handle  24  by an operator, the pin  70  is biased by the spring  60  against the flat wall  100  of the aperture  80 ′ at he centre of the flat wall  100 , with equal space within the aperture  80 ′ being left on either side of the pin  70  in the direction of the flat wall  100  as shown in  FIGS. 7 and 8 . Movement of the pin  70  in the aperture  80 ′, in any direction from the central position against the flat wall  100  is against the biasing force of the spring  60 . 
         [0054]    Vibrations in the second direction result in a twisting movement of the housing  2 , motor  6  and the rotary drive and hammer mechanism  10  about the centre of gravity axis  120 . As the pin  70  is located in the semi-circular slot  80 ′ of the insert  78  which is orientated so that the flat wall  100  of the aperture  80 ′ extends (Arrow N) tangentially to a circle centered on the centre of gravity axis  120  in a lengthwise vertical plane, the pin  70  can slide tangentially relative to the centre of gravity axis  120  along the flat wall  100 , allowing housing  2 , motor  6  and the rotary drive and hammer mechanism  10  to twist about the centre of gravity axis  120  relative to the rear handle  24 . This twisting movement is then damped due to the action of the spring  60  in the upper mounting mechanism  32  which biases the pin  70  against and to the centre of the flat wall  100 . 
         [0055]    However, the pin  70  is also allowed to move within the aperture away from the flat wall  100  towards the circular wall  102  against the biasing force of the spring  60 . This assists in the in dampening vibrations in the first direction as, in addition to the rear handle  12  pivoting about the pin  70  in the lower mounting assembly  36  when it is engaged with either the flat wall  100  or semi circular wall  102  (or both) of the aperture  80 ′, it can move linearly sideways within the aperture  80 ′ allowing a limited linear movement of the lower end  32  of the handle  24  relative to the rear housing  12 . 
         [0056]    Whilst the two embodiments described relate to hammer drills, it will be appreciated by the reader that the invention as claimed could relate to a range of different types of power tools.