FIELD OF THE INVENTION

[0001] The present invention relates to impact mechanisms impact apparatuses, and more particularly to such impact mechanisms that are efficient at producing impact torque and impact force.

BACKGROUND OF THE INVENTION

[0002] Impact apparatuses are used to forcefully turn threaded fasteners that are otherwise difficult to turn when driving threaded fasteners into a substrate. Such difficulty in turning threaded fasteners is typically encountered when driving them into a substrate such as concrete, but can be encountered in many other situations, especially in the construction industry.

[0003] The effectiveness of an impact apparatus is directly related to the impact torque supplied by the impact mechanism used in the impact apparatus and indirectly by the drive motor, such as a drive motor found in an electric drill. For years, the entire power tool industry has sought to develop better impact apparatuses that are capable of delivering a greater amplitude of impact torque by increasing the torque of the drive motor, and by increasing the spring force of the power spring, which is typically, a coil spring.

[0004] In order to maximize impact torque, prior art impact apparatuses employ impact mechanisms that have a maximum distance between the anvil lobes in order to give the drive motor and the power spring as much time as possible to rotationally accelerate the hammer member. Accordingly, known prior art impact mechanisms have two diametrically opposed hammer lobes that act on two diametrically opposed anvil lobes. Although it is theoretically possible to have only one hammer lobe and one anvil lobe in order to maximize the distance, between consecutively impacted anvil lobes the unbalanced forces that would be created during use make this configuration impractical.

[0005] The problem with the approach of having two diametrically opposed hammer lobes that act on two diametrically opposed anvil lobes is that part way through the arcuate distance travelled by each hammer lobe between one anvil lobe and the next, the accelerative force of the power spring may be relatively low or even non existent. In other words, the power spring is not used as effectively as possible.

[0006] In addition to be able to turn fasteners using strong impact pulses, it is also very useful, and even necessary in many cases, to be able to control the impact force that is imparted to the threaded fastener being turned. Such control is necessary to set threaded fasteners to a predetermined torque in order to meet specified standards and also to preclude threaded fasteners from being driven too far into a substrate or from over-torqueing and placing too high a tensile load on fasteners such as to fatigue the metal and eliminate its clamp capacity and sheer force resistance, and even to preclude threaded fasteners from breaking during installation. Such control generally requires accurately pre-set torque and low torque forces.

[0007] Unfortunately, these two criteria, namely the strength of impact pulses and the control of impact pulses, especially at low torque settings, appear to be substantially conflicting. Accordingly, it is unknown in the prior art to have an impact apparatus that can provide both low and high impact torque and control of impact torque throughout a large range of impact torque, in spite of the fact that leading fastener companies and tool companies have been trying to develop such an impact apparatus for years.

[0008] It is an object of the present invention to provide animpact mechanism that is operatively engageable with the chuck of an electric drill or the like, which impact mechanism provides a high impact rotational force.

[0009] It is an object of the present invention to provide an impact mechanism that is operatively engageable with the chuck of an electric drill or the like, which impact mechanism provides a high impact rotational force, and which impact mechanism works from low impact forces through high impact forces. [00010] It is an object of the present invention to provide an impact mechanism that is operatively engageable with the chuck of an electric drill or the like, which impact mechanism provides a high impact rotational force, and which impact mechanism may be readily adjustable from low impact forces through high impact forces.

[00011] It is an object of the present invention to provide an impact mechanism that is operatively engageable with the chuck of an electric drill or the like, which impact mechanism provides a high impact rotational force, and which impact mechanism may be accurately settable adjustable from low impact forces through high impact forces.

[00012] It is an object of the present invention to provide an impact mechanism that is operatively engageable with the chuck of an electric drill or the like, which impact mechanism permits setting to a predetermined torque such that threaded fasteners can be properly installed in order to meet specified standards.

[00013] It is an object of the present invention to provide an impact mechanism that is operatively engageable with the chuck of an electric drill or the like, which impact mechanism precludes threaded fasteners from being driven too far into a substrate.

[00014] It is an object of the present invention to provide an impact mechanism that is operatively engageable with the chuck of an electric drill or the like, which impact mechanism precludes threaded fasteners from breaking during installation. SUMMARY OF THE INVENTION

[00015] In accordance with one aspect of the present invention there is disclosed a novel impact mechanism for use with a drive motor. The impact mechanism comprises a drive shaft defining a longitudinal axis, and operatively carrying a hammer member for rotational movement about the longitudinal axis and longitudinal movement between a forward position and a rearward position that define a longitudinal clearing displacement therebetween, and operatively carrying an anvil member for rotational movement about the longitudinal axis. The hammer member has first, second and third hammer lobes spaced radially around the longitudinal axis. The anvil member has first, second and third anvil lobes spaced radially around the longitudinal axis, to define an overall travel arc between impact faces of adjacent anvil lobes. A spring is operatively interconnected between the drive shaft and the hammer member for temporarily storing energy from the relative rotation of the drive shaft with respect to the hammer member and subsequently releasing stored energy to forcibly rotate the hammer member about the longitudinal axis with respect to the anvil member. A tool retainer is connected in torque transmitting relation to the anvil member for rotation therewith. As the hammer member is rotated by the spring and the drive shaft with respect to the anvil member, the hammer member and the anvil member go through consecutive impact cycles wherein the hammer lobes are initially in lateral engagement with the anvil lobes, the hammer lobes move rearwardly with respect the longitudinal axis through the longitudinal clearing displacement to be longitudinally positioned to subsequently permit the spring to forcefully rotate the hammer past the engaged anvil lobes, and subsequently to forcefully impact the rotationally next ones of the anvil lobes, to thereby create the corresponding impact torque for the anvil member about the longitudinal axis.

[00016] Other advantages, features and characteristics of the present invention, as well as methods of operation and functions of the related elements of the structure, and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following detailed description and the appended claims with reference to the accompanying drawings, the latter of which is briefly described herein below.

BRIEF DESCRIPTION OF THE DRAWINGS

[00017] The novel features which are believed to be characteristic of the impact mechanism according to the present invention, as to its structure, organization, use and method of operation, together with further objectives and advantages thereof, will be better understood from the following drawings in which a presently preferred embodiment of the invention will now be illustrated by way of example. It is expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. In the accompanying drawings:

[00018] Figure 1 is a side elevational view from the front of the first illustrated embodiment of the impact mechanism according to the present invention;

[00019] Figure 2 is a perspective view from the back end of the first illustrated embodiment of the impact mechanism of Figure 1;

[00020] Figure 3 is a back end elevational view of the first illustrated embodiment of the impact mechanism of Figure 1;

[00021] Figure 4 is a perspective view from the front of the first illustrated embodiment of the impact mechanism of Figure 1, with a tool bit, specifically a socket, operatively engaged thereon, with the hammer member in a forward position with respect to the anvil member;

[00022] Figure 5 is a perspective view from the front of the first illustrated embodiment of the impact mechanism of Figure 1, with the hammer member in a forward position with respect to the anvil member and just about to start an impact cycle; [00023] Figure 6 is a perspective view from the front of the first illustrated embodiment of the impact mechanism of Figure 1, with the hammer member in a rearward position with respect to the anvil member and having just started an impact cycle;

[00024] Figure 7 is a perspective view from the front of the first illustrated embodiment of the impact mechanism of Figure 1 and similar to Figure 6, but with the hammer member having moved rotationally such that the hammer lobes have moved almost all the way across the anvil lobes and about be propelled forcefully to the next anvil lobes;

[00025] Figure 8 is a front-end view of the hammer member of the second illustrated embodiment of the impact mechanism according to the present invention; and,

[00026] Figure 9 is a graph showing the torque, as recorded in tests, achieved by various configurations of impact mechanisms according to the present invention and also by prior art impact mechanisms.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[00027] Referring to Figures 1 through 9 of the drawings, it will be noted that Figures 1 through 7show a first illustrated embodiment of the impact mechanism according to the present invention, Figure 8shows a second illustrated embodiment according to the impact mechanism of the present invention, and Figure 9 shows a graph showing the torque, as recorded in tests, achieved by various configurations of impact mechanisms according to the present invention and also by prior art impact mechanisms.

[00028] Reference will now be made to Figures 1 through 7, which show a first illustrated embodiment of the impact mechanism according to the present invention, as indicated by general reference numeral 100. The impact mechanism 100 is part of an impact apparatus (the housing is not shown) for use with a drive motor (not specifically shown), such as the drive motor of an electric drill (not specifically shown). Any other suitable drive mechanism could be used.

[00029] The impact mechanism 100 comprises a drive shaft 120 that engages a rotatable output, namely the chuck of the electric drill. The chuck-engageable back end portion 122 of the drive shaft 120 is preferably hexagonally shaped (as best seen in Figure 4), or of any other suitable shape, for secure engagement into the chuck of the electric drill for rotation therewith. The chuck is rotationally driven by the drive motor of the electric drill for rotation therewith about a longitudinal axis “L” about which the drive shaft 120 rotates.

[00030] The drive shaft 120 defines the longitudinal axis “L” and operatively carries a hammer member 130 and an anvil member 140 as will be described in greater detail subsequently.

[00031] The hammer member 130 has a first hammer lobe 131, a second hammer lobe 132, a third hammer lobe 133, and a fourth hammer lobe 134. The first hammer lobe 131, the second hammer lobe 132, the third hammer lobe, and the fourth hammer lobe 134 are spaced equally radially around the longitudinal axis “L”. As illustrated, the angular displacement around the longitudinal axis “L” of the centre of the first hammer lobe 131, the centre of the second hammer lobe 132, and the centre of the third hammer lobe 133, and the fourth hammer lobe 134, with respect to the adjacent hammer lobes is ninety (90) degrees. The ratio of the arcuate width 139b of the base137b of each hammer lobe 131,132,133,134about the longitudinal axis to the arcuate width 139t of the tip 137t of each hammer lobe 131,132,133,134 about the longitudinal axis “L” is between about 2:1 and 4:1.

[00032] Similarly, the anvil member 140 has a first anvil lobe 141, a second anvil lobe 142, a third anvil lobe 143, and a fourth anvil lobe 144. The first anvil lobe 141, the second anvil lobe 142, the third anvil lobe 143, and the fourth anvil lobe 144 are spaced equally radially around the longitudinal axis “L”. As illustrated, the angular displacement around the longitudinal axis “L” of the centre of the first anvil lobe 141 , the centre of the second anvil lobe 142, and the centre of the third anvil lobe 143, and the fourth anvil lobe 144, with respect to the adjacent hammer lobes is ninety (90) degrees. The ratio of the arcuate width 149b of the base147b of each anvil lobe141,142,143,144about the longitudinal axis“L” to the arcuate width 149t of the tip147t of each anvil lobe 141 ,142,143,144 about the longitudinal axis is between about 2:1 and 4:1.

[00033] The drive shaft 120 defines the longitudinal axis “L” and operatively carries the hammer member 130 for rotational movement of the hammer member 130 about the longitudinal axis “L” and also for longitudinal movement of the hammer member 130 between a forward position, as is best seen in Figures 1 through 5, and a rearward position, as is best seen in Figures 6 and 7. The forward position and the rearward position together define a longitudinal clearing displacement “LCD” therebetween. The longitudinal clearing displacement “LCD” is the distance that the hammer member 130 needs to travel longitudinally rearwardly along the longitudinal axis “L” to get the hammer lobes 131, 132, 133, 134 past the anvil lobes 141, 142, 143, 144.

[00034] The displacement of the centre of the hammer lobes 131, 132, 133, 134 and of the centre of the anvil lobes 141, 142, 143, 144 from the central longitudinal axis “L” defines an arc of overall travel (overall travel arc) of the hammer member 130 about the longitudinal axis “L” with respect to the anvil member 140 between consecutive impacts, as indicated by the reference letters ΌT”. [00035] As the hammer member 130 is rotated by the drive shaft 120 with respect to the anvil member 140, around the longitudinal axis “L”, the first hammer lobe 131, the second hammer lobe 132, the third hammer lobe 133, and the fourth hammer lobe 134 each impact the first anvil lobe 141, the second anvil lobe 142, the third anvil lobe 143, and the fourth anvil lobe 144. More specifically, the first hammer lobe 131 consecutively impacts the first anvil lobe 141, the second anvil lobe 142, the third anvil lobe 143, and the fourth anvil lobe 144. Concurrently, the second hammer lobe 132 consecutively impacts the second anvil lobe 142, the third anvil lobe 143, the fourth anvil lobe 144, and the first anvil lobe 141. Also concurrently, the third hammer lobe 133 consecutively impacts the third anvil lobe 143, the fourth anvil lobe 144, the first anvil lobe 141, and the second anvil lobe 142. Also concurrently, the fourth hammer lobe 134 consecutively impacts the fourth anvil lobe 144, the first anvil lobe 141, the second anvil lobe 142, and the third anvil lobe 143.

[00036] The impacting of the hammer lobes 131,132,133,134 on the anvil lobes 141,142,143,144 creates corresponding impact torque for the anvil member 140 about the longitudinal axis “L”.

[00037] There is also a power spring 160 operatively interconnected between the drive shaft 120 and the hammer member 130 for temporarily storing energy from the relative rotation of the drive shaft 120 with respect to the hammer member 130 and subsequently releasing stored energy to forcibly rotate the hammer member 130 about the longitudinal axis “L” with respect to the anvil member 140. In other words, the power spring 160 provides stores potential energy to thereby provide kinetic energy for the impact forces to be transmitted from the hammer lobes 131,132,131,134 to the anvil lobes 141,142,143,144. Further, the power spring 160 biases the hammer member 130 at least towards the forward longitudinal position and preferably to the forward longitudinal position.

[00038] As the hammer member 130 is rotated by the power spring 160 and the drive shaft 120 with respect to the anvil member 140, the hammer member 130 and the anvil member 140 go through consecutive impact cycles wherein the hammer lobes 131, 132, 133, 134 are initially in lateral engagement with the anvil lobes 141, 142, 143, 144. The hammer lobes 131, 132, 133, 134 move rearwardly along the longitudinal axis “L” through the longitudinal clearing displacement “LCD” to be longitudinally positioned to rotationally move past the engaged anvil lobes 141, 142, 143, 144 and subsequently to forcefully impact the rotationally next ones of the anvil lobes 141, 142, 143, 144, to thereby create the corresponding impact torque for the anvil member 140 about the longitudinal axis “L”, to thereby rotationally drive a threaded fastener.

[00039] As can be readily seen in the Figures, the ratio of the overall travel arc “OT” to the longitudinal clearing displacement “LCD” is less than about 4:1. [00040] Each of the hammer lobes 131, 132, 133, 134 has a first face 136 and a second face 138 and each of the anvil lobes 141, 142, 143, 144 has a first face 146 and a second face 148. As viewed from the back, such as in Figures 2 and 3, the first faces 136 of the hammer lobes 131, 132, 133, 134 and the first faces 146 of the anvil lobes 141, 142, 143, 144 all face in a clockwise direction. Further, the second faces 138 of the hammer lobes 131, 132, 133, 134 and the second faces 148 of the anvil lobes 141, 142, 143, 144 all face in a counterclockwise direction. Also, the arcuate width 149t of the tip147t of each anvil lobel 41 , 142, 143, 144 about the longitudinal axis “L” to the arcuate distance 170 between the first face 146 of one anvil lobe, such as the first anvil lobe 141, and the second face 148 of the adjacent anvil lobe, such as the fourth anvil lobe 144, is between about 5:1 and 15:1. Further, the ratio of the arcuate width 139b of the base139b of the each hammer lobe 131, 132,133, 134about the longitudinal axis “L” to the arcuate width 139t of the tip 137t of each hammer lobe 131,132,133,134 about the longitudinal axis “L” is between about 2:1 and 4:1. Further, the ratio of the arcuate width 149b of the base 147b of each anvil lobe 141, 142, 143, 144 about the longitudinal axis“L” to the arcuate width 149t of the tip 147t of each anvil lobe 141, 142, 143, 144 about the longitudinal axis “L” is between about 2:1 and 4:1.

[00041] The first faces 146 and the second faces 148 of the anvil lobes 141,142,143,144 are oriented so as to be skew with respect to the longitudinal axis “L” and the first faces 136 and the second faces 136 of the hammer lobes 131,132,133,134 are oriented so as to be skew with respect to the longitudinal axis “L”. [00042] The drive shaft 120 also operatively carries an anvil member 140 for rotational movement about the longitudinal axis “L”. A tool retainer 150 is securely connected in torque transmitting relation to the anvil member 140 for rotation therewith. As can be seen in Figure 4, a socket 152 is removably mounted on the tool retainer 150.

[00043] There are two important considerations in terms of the rotational travel of the hammer lobes 131, 132, 131, 134 around the longitudinal axis “L” as they impact the anvil lobes 141, 142, 143, 144. One consideration is the arc of overall travel of the hammer member 130 about the longitudinal axis “L” with respect to the anvil member 140 between consecutive impacts, as indicated by the reference letters “OT”. The second is the arc of free travel of the hammer member 130, as indicated by the reference letters “FT”, about the longitudinal axis “L” when the second face 138 of each hammer lobe 131, 132, 133, 134 rotationally passes the first face 146 of the anvil lobes 141, 142, 143, 144 to the next impact with the anvil lobes 141, 142, 143, 144, whereat the first face 136 of each hammer lobe 131, 132, 133, 134 impacts the second face 148 of each anvil lobe 141, 142, 143, 144.

[00044] In use, when the hammer member 130 is rotated in a first rotational direction about the longitudinal axis “L” with respect to the anvil member 141, 142, 143, 144, which is a clockwise direction as indicated by arrow “CW”, the first face 136 of each hammer lobe 131, 132, 133, 134 contacts the second face 148 of a corresponding anvil lobe 141, 142, 143, 144. When the hammer member 130 is rotated in a second rotational direction about the longitudinal axis “L” with respect to the anvil member 140, which is a counter clockwise direction as indicated by arrow “CCW’, the second face 138 of each hammer lobe 131, 132, 133, 134 contacts the first face 146 of a corresponding anvil lobe 141, 142, 143, 144.

[00045] The ratio of the arc of free travel of the hammer member 130, as indicated by the reference letters “FT”, about the longitudinal axis “L” when the second face 138 of each hammer lobe 131, 132, 133, 134 rotationally passes the first face 146 of the anvil lobes 141, 142, 143, 144 to the next impact with the anvil lobes 141, 142, 143, 144, whereat the first face 136 of each hammer lobe 131, 132, 133, 134 impacts the second face 148 of each anvil lobe 141, 142, 143, 144, to the arc of overall travel of the hammer member 130 about the longitudinal axis “L” with respect to the anvil member 140 between consecutive impacts, as indicated by the reference letters ΌT”, and also known as the overall travel arc, is less than about 3:4 and is even less than about 2:3.

[00046] Reference will now be made to Figure 8, which shows a second illustrated embodiment of the impact mechanism according to the present invention, as indicated by general reference numeral 200. The second illustrated embodiment impact mechanism 200 is similar to the first illustrated embodiment impact mechanism 100, except that in the second illustrated embodiment impact mechanism 200, the hammer member230 has only a first hammer lobe 231, a second hammer lobe 232, a third hammer lobe 233, but not a fourth hammer lobe. The first 231, second 232, and third 233 hammer lobes are spaced equally radially around the longitudinal axis “L”. The angular displacement around the longitudinal axis “L” of the centre of the first hammer lobe 231, the centre of the second hammer lobe 232, and the centre of the third hammer lobe 232 with respect to the adjacent hammer lobes is one hundred twenty (120) degrees. Similarly, the anvil member (not specifically shown) has only a first anvil lobe, a second anvil lobe, a third anvil lobe, but not a fourth anvil lobe. The first, second, and third anvil lobes are spaced equally radially around the longitudinal axis “L”. The angular displacement around the longitudinal axis “L” of the centre of the first anvil lobe, the centre of the anviL lobe, and the centre of the third anvil lobe with respect to the adjacent anvil lobes is one hundred twenty (120) degrees.

[00047] The displacement of the centre of the hammer lobes 231, 232, 233 of the centre of the anvil lobes from the central longitudinal axis “L” defines an arc of overall travel of the hammer member 230 about the longitudinal axis “L” with respect to the anvil member 240 between consecutive impacts, as indicated by the reference letters

“OT”.

[00048] The ratio of the arc of free travel of the hammer member 230, as indicated by the reference letters “FT”, about the longitudinal axis“L”is less than about 3:4. [00049] Reference will now be made to Figure 9, which shows a graph of torque vs. RPM for impact mechanisms according to the present invention having three (3) hammer lobes on the hammer member and three (3) anvil lobes on the anvil member, having four (4) hammer lobes on the hammer member and four (4) anvil lobes on the anvil member, and five (5) hammer lobes on the hammer member and five (5) anvil lobes on the anvil member, as compared to prior art impact mechanisms that have two (2) hammer lobes on the hammer member and two (2) anvil lobes on the anvil member. These results were recorded as a result of tests of various configurations of impact mechanisms according to the present invention andalso by prior art impact mechanisms. It can readily be seen that more hammer lobes produce greater torque at a normal RPM range.

[00050] It can be readily seen that there is more impact torque available for impact mechanism having three (3) hammer lobes on the hammer member and three (3) anvil lobes on the anvil member, having four (4) hammer lobes on the hammer member and four (4) anvil lobes on the anvil member, and five (5) hammer lobes on the hammer member and five (5) anvil lobes on the anvil member, as compared to prior art impact mechanisms that have two (2) hammer lobes on the hammer member and two (2) anvil lobes on the anvil member.

[00051] As can be understood from the above description and from the accompanying drawings, the present invention provides an impact mechanism that is operatively engageable with the chuck of an electric drill or the like, which impact mechanism provides a high impact rotational force, which impact mechanism works from low impact forces through high impact forces, which impact mechanism is readily adjustable from low impact forces through high impact forces, which impact mechanism is accurately settable adjustable from low impact forces through high impact forces, which impact mechanism permits setting to a predetermined torque such that threaded fasteners can be properly installed in order to meet specified standards, which impact mechanism precludes threaded fasteners from being driven too far into a substrate, which impact mechanism precludes threaded fasteners from breaking during installation, all of which features are unknown in the prior art.

[00052] Other variations of the above principles will be apparent to those who are knowledgeable in the field of the invention, and such variations are considered to be within the scope of the present invention. Further, other modifications and alterations may be used in the design and manufacture of the impact mechanism of the present invention without departing from the spirit and scope of the accompanying claims.