CON ROD

Abstract

A hammer drill is provided including a housing, a motor mounted within the housing, and a hammer mechanism. The hammer mechanism includes a crank plate or a wobble plate driven by the motor, a con rod coupled to the crank plate or the wobble plate, a piston reciprocatingly driven by the con rod along a longitudinal axis, a ram and a beat piece. At least one of the wobble plate or the con rod is made of sintered steel.

Claims

1. A hammer drill comprising: a housing; a tool holder mounted on the housing and configured to hold a cutting tool; a motor mounted within the housing; and a hammer mechanism comprising: a crank plate; a con rod pivotally connected at a first end to the crank plate, the con rod being made of sintered steel in a one-piece construction; a piston slidably mounted in the housing and reciprocatingly driven along a longitudinal axis by the motor via the crank plate and con rod, wherein a second end of the con rod is pivotally connected to the piston; a ram mounted in the housing forward of the piston that is reciprocatingly driven along the longitudinal axis by the piston via an air spring; and a beat piece supported in an axially sliceable manner along the longitudinal axis within a beat piece support structure, wherein during the normal operation of the hammer mechanism, the beat piece is repetitively struck by the ram and transfers impact energy to the cutting tool.

2. The hammer drill of claim 1, wherein the hammer mechanism comprises a cylinder, and wherein the piston is mounted in the cylinder and the ram is mounted in the cylinder forward of the piston.

3. The hammer drill of claim 2, wherein the cylinder is made from sintered steel.

4. The hammer drill of claim 2, wherein the cylinder is formed as a part of a spindle.

5. The hammer drill of claim 1, wherein the con rod is impregnated with a lubricant.

6. The hammer drill of claim 5, wherein the lubricant comprises at least one of oil or grease.

7. The hammer drill of claim 1, wherein the con rod comprises a central section that interconnects two end ring sections, wherein the central section includes a rectangular cross-section with an elongate groove extending in a lengthwise direction along each of the sides of the central section, and wherein each of the two end ring sections comprises a circular aperture.

8. The hammer drill of claim 7, wherein the con rod comprises a semi-circular groove formed in a side wall of at least one of the apertures of the two end sections.

9. The hammer drill of claim 1, wherein the con rod is pivotally connected at the first end to the crank plate via an eccentric pin made from sintered steel.

10. The hammer drill of claim 9, wherein the eccentric pin is impregnated with a lubricant.

11. The hammer drill of claim 1, wherein the con rod is pivotally connected at the second end to the piston via a cross pin made from sintered steel.

12. The hammer drill of claim 11, wherein the cross pin is impregnated with a lubricant.

13. A hammer drill comprising: a housing; a tool holder mounted on the housing and configured to hold a cutting tool; a motor mounted within the housing; and a hammer mechanism comprising: a wobble plate driven by the motor, the wobble plate being at least partially made of sintered steel; a con rod pivotally including a first end coupled to the crank plate and a second end; a piston slidably mounted in the housing and coupled to the second end of the con rod, the piston being reciprocatingly driven along a longitudinal axis by the motor via the wobble plate and the con rod; a ram mounted in the housing forward of the piston that is reciprocatingly driven along the longitudinal axis by the piston via an air spring; and a beat piece supported in an axially sliceable manner along the longitudinal axis within a beat piece support structure, wherein during the normal operation of the hammer mechanism, the beat piece is repetitively struck by the ram and transfers impact energy to the cutting tool.

14. The hammer drill of claim 13, wherein the wobble plate comprises: a circular central plate; a ring mounted on the circular central plate that surrounds a periphery of the circular central plate such a plane of the ring is parallel to a plane of the circular central plate, the ring being able to freely rotate around the periphery of the circular central plate; and a finger attached to a side of the ring and extending radially away from a centre of the ring; wherein at least one of the circular central plate, the ring, or the finger is made from sintered steel.

15. The hammer drill of claim 14, wherein at least one of the circular central plate, the ring, or the finger is impregnated with a lubricant.

16. The hammer drill of claim 15, wherein the lubricant is at least one of oil or grease.

17. The hammer drill of claim 13, wherein the con rod is made of sintered steel in a one-piece construction.

18. The hammer drill of claim 17, wherein the con rod comprises a central section that interconnects two end ring sections, wherein the central section includes a rectangular cross-section with an elongate groove extending in a lengthwise direction along each of the sides of the central section, and wherein each of the two end ring sections comprises a circular aperture.

19. The hammer drill of claim 18, wherein the con rod comprises a semi-circular groove formed in a side wall of at least one of the apertures of the two end sections.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations and are not intended to limit the scope of the present disclosure.

[0036] FIG. 1 shows a sketch of a side view of a prior art hammer drill;

[0037] FIG. 2 shows a cross sectional view of the hammer mechanism with the ram in a position where it can freely slide within the spindle;

[0038] FIG. 3 shows a cross sectional view of the hammer mechanism with the ram in the ram catcher and the beat piece sliding in the spindle;

[0039] FIG. 4 shows a cross sectional view of the hammer mechanism with the ram in the ram catcher and the beat piece in its furthest forward position in the spindle;

[0040] FIG. 5 shows the beat piece;

[0041] FIG. 6 shows a vertical cross-sectional view of a hammer drill in accordance with a first embodiment the present invention;

[0042] FIG. 7 shows a rear view of the piston shown in FIG. 6;

[0043] FIG. 8 shows a side view of the piston shown in FIG. 6;

[0044] FIG. 9 shows a rear perspective view of the piston shown in FIG. 6;

[0045] FIG. 10 shows a front perspective view of the piston shown in FIG. 6;

[0046] FIG. 11 shows a side view of the con rod of FIG. 6;

[0047] FIG. 12 shows a cross sectional view of the con rod in the direction of Arrows A in FIG. 11;

[0048] FIG. 13 shows a cross sectional view of the con rod in the direction of Arrows B in FIG. 11; and

[0049] FIG. 14 shows a second embodiment of the present invention.

[0050] Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION

[0051] Two embodiments of the present invention will now be described with reference to FIGS. 6 to 14.

[0052] FIG. 6 shows a cross section view of hammer drill having a con rod in accordance with a first embodiment of the present invention. Where the same features in the embodiment shown in FIG. 6 are shown in the prior art example described above, the same reference numbers are used and the same description is applicable. The main difference between the prior art design and the embodiment is the design of the con rod 206, the piston 204 and hollow spindle 150.

[0053] Referring to FIG. 6, the hammer mechanism comprises a first gear 400 rotationally driven by an electric motor (not shown). The first gear 400 is rigidly attached to a first spindle 402 such rotation of the first gear 400 results in rotation of a spindle 402.

[0054] A second gear 406 is mounted on the first spindle 402 adjacent the first gear. The second gear 406 is axially fixed on the first spindle 402 but can freely rotate around the first spindle 402. A crank plate 408 is mounted on a top end of the first spindle 402. The crank plate 408 is axially fixed on the spindle but can freely rotate around the end of the spindle 402.

[0055] A sleeve 404 is mounted on the spindle 402 and surrounds a splined section 410 of the first spindle 402. The inner part of the sleeve 404 comprises corresponding splines which engage with the splines of the spindle 402. The sleeve 404 can axially slide along the first spindle 402 but is rotationally fixed to the first spindle 402 via the meshing splines so that rotation movement of the sleeve 404 always results in rotational movement of the spindle 402. The sleeve 404 can slide vertically between three positions; a lower position where it in driving engagement with spline section 410 and the second gear 406 only; a middle position where it is driving engagement with the spline section 410, the second gear 406 and the crank plate 408; and an upper position where it in driving engagement with the spline section 410 and the crank plate 408 only. The sleeve 404 is moved between its three positions via a mode change mechanism 412 which is operated using a mode change knob 414.

[0056] The second gear 406 is in driving engagement with a third gear 416 which is mounted on a second spindle 418. Rotation of the second gear 406 results in rotation of the third gear 416. The third gear 416 is axially fixed on the second spindle 418. The third gear 416 is rotationally fixed to the second spindle 418 via a torque clutch 420 so that rotation of the third gear 416 results in rotation of the second spindle 418 if the torque across the torque clutch 420 is below a pre-set value and that rotation of the third gear 416 results in rotation of the third gear 416 around the second spindle 418 if the torque across the torque clutch is above a pre-set value with the second spindle remaining stationary.

[0057] A first bevel gear 422 is formed on the top end of the second spindle 418, the first bevel gear 422 is in driving engagement with a second bevel gear 424 which surround and is rigidly connected to the hollow spindle 150. Rotation of the second spindle 418 results in rotation of the hollow spindle 150 via the bevel gears 422, 424.

[0058] The crank plate 408 has an eccentric pin 426 integrally formed on the top of the crank plate 408. The longitudinal axis of the eccentric pin 426 is parallel to but offset from longitudinal axis of the first spindle 402 such rotation of the first spindle 402 results in the eccentric pin 426 rotating around the longitudinal axis of the first spindle 402, the eccentric pin 426 moving back and forwards as well as side to side as it does so. A con rod 206 connects between the eccentric pin 426 and the piston 204 inside of the hollow spindle. Rotation of the crank plate 308 results in the reciprocation of the piston 204 within the hollow spindle 150.

[0059] Referring to FIGS. 7 to 10, the piston 204 is a flat piston and comprises a front circular disk 300 having flat front surface 302. A circumferential groove 304 extends around the edge of the circular disk 300. A circular peripheral wall 306 extends rearwardly from the edge of the circular disk 300, perpendicularly to the plane of the circular disk 300. Two straight sections 308 are formed on two opposite sides of the wall 306. A frame 310 is formed on each straight section 308. An aperture 314 is formed through each frame 310 and straight section 308. The piston 204 is manufactured in a one-piece construction from sintered steel which has been impregnated with a lubricant such as grease and/or oil.

[0060] The rubber O ring 208 locates in the groove 304. The piston 204 is mounted inside of the hollow spindle 150 and connected to the con rod 206 via a cross pin 312.

[0061] The con rod 206 is shown in more detail in FIGS. 11 to 13. The con rod comprises a central section 440 which interconnects two end ring sections 442, 444. The central section 440 is of rectangular cross section with an elongate groove 446, 448 extending in a lengthwise direction along each of the sides of the central section 440. Each end ring section comprises a circular aperture 450, 452. One end section 442 connects to the eccentric pin 426, the eccentric pin 426 locating inside of the circular aperture 450 of the end section 442. The other end section 444 connects to the cross pin 312 for the piston 204, the cross pin 312 locating inside of the circular aperture 452 of the end section 444. A semi-circular groove 460 is formed in the side wall of each aperture 450, 452 along the length of the apertures 450, 452. The con rod 206 is manufactured in a one-piece construction from sintered steel which has been impregnated with a lubricant such as grease and/oil. The impregnated lubricant reduces the friction between the con rod 206 and the eccentric pin 426 and cross pin 312 as the eccentric pin 426 and cross pin 312 pivot within the apertures 450, 452 during the operation of the hammer mechanism. The semi-circular grooves 460 enable addition additional lubrication to enter the apertures 450, 452 and engage with the surfaces of the apertures 450, 452, eccentric pin 426 and cross pin 312 making friction contact.

[0062] It will be appreciated that the eccentric pin 426 and/or cross pin 312 could be manufactured in a one-piece construction from sintered steel which has been impregnated with a lubricant such as grease and/or oil. This would further help lubrication to reduce the frictional contact. If the eccentric pin 426 and crank plate 408 are manufactured in one-piece construction, then both of these can be manufactured in a one-piece construction from sintered steel which has been impregnated with a lubricant such as grease and/or oil.

[0063] The design of the hollow spindle 150 is manufactured from steel. The coefficient of expansion of the steel hollow spindle 150 is the same as that of the sintered flat piston 204.

[0064] Alternatively, the hollow spindle 150 is manufactured from sintered steel. Ideally, it would be manufactured in a one-piece construction. The coefficient of expansion of the sintered steel hollow spindle 150 is the same as that of the sintered flat piston 204. The sintered steel hollow spindle 150 can impregnated with a longitudinal axis of the first spindle lubricant such as grease and/oil.

[0065] The sintered con rod 206, the sintered steel piston 204 and/or the sintered steel hollow spindle 150 can be manufactured by using a sintering process and then submersing them in a lubricant, such as a grease and/or oil, to impregnate the con rod and/or piston and/or spindle with the lubricant.

[0066] A second embodiment of the present invention will now be described with reference to FIG. 14. Where the same features in the second embodiment are present in the first embodiment, the same reference numbers have been used. The difference between the first embodiment and the second embodiment is that the crank plate and eccentric pin have been replaced with a wobble plate.

[0067] The wobble plate comprises a circular central plate 500 mounted on a shaft 502, the plane of the plate 500 being located at an angle 504 relative to a longitudinal axis 506 of the shaft 502. The shaft 502 is driven by the first spindle 402 via set of bevel gears 508. A circular ring 510 is mounted on the plate 500 via a bearing 512 and surrounds the periphery of the plate 500 such that plane of the ring 510 is parallel to the plane of the plate 500. The ring 510 can freely rotate around the periphery of the plate 500. The ring 510 is prevented from rotating. Therefore, as the shaft 502 rotates, the plane of the plate 500 oscillates back and forth in the direction of the longitudinal axis 506 of the shaft 502. A finger 514 is attached to the side of the ring 510 and extends radially away from the centre of the ring 510. The end of the finger 514 remote from the ring 510 is attached to the rear of the piston 204 via a con rod 206. As the shaft 502 rotates and the plane of the plate 500 oscillates back and forth in the direction of the longitudinal axis 506 of the shaft 502, the finger 514 also oscillates back and forth in the direction of the longitudinal axis 506 of the shaft 502, reciprocatingly driving the piston 204.

[0068] The ring 510 and finger 514 is manufactured in a one-piece construction from sintered steel which has been impregnated with a lubricant such as oil. The impregnated lubricant reduces the friction between the ring 510 and the bearing 512 and between the finger 514 and the con rod 206. The plate and shaft can also be manufactured in a one-piece construction from sintered steel which has been impregnated with a lubricant such as oil. With the reduction in friction, it will be appreciated that the bearing 512 can be omitted, with the ring 510 being directly rotationally mounted on the plate 500.

[0069] Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

[0070] The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.