Gear shifting mechanism for selecting between different modes of operation in a hand-held power tool

Abstract

The invention relates to a gear shifting mechanism for selecting between different operating modes in an electric hand tool, comprising a manually operable rotary selector switch (1) for adjusting the angle of a shift rod (2) provided with a shift cam (3), which acts on subsequent gear elements via molded-on actuating cams to set a desired operating mode, wherein cooperating spring elements are provided for locking the shift rod (2) in the selected shift position, wherein the spring elements are designed as a combined spring arrangement, comprising at least a first spring element (6) of a first spring type, which is arranged in the chain of action between the rotary selector switch (1) and the shift rod (2), and at least a second spring element (7) of a second spring type.which interacts with the shift gate (3) of the shift rod (2) in corresponding detent positions to lock a selected shift position.

Description

[0001] The present invention relates to a gear shifting mechanism for selecting between different operating modes in an electric hand tool, comprising a manually operable rotary selector switch for adjusting the angle of a shift rod provided with a shift cam, which acts on subsequent gear means via molded-on actuating cams to set a desired operating mode, wherein cooperating spring means are provided for locking the shift rod in the selected shifting position.

[0002] The application area of ​​the present invention relates primarily to power tools that can be operated in different modes. For example, a rotary hammer can be switched between drilling, impact drilling, or chiseling modes. Usually, an additional mode for positioning the chisel is also provided. Switching between such modes is typically accomplished via a manually operated switch located on the housing of the power tool, using a gear mechanism. Such a switch can be designed as a slide switch or as a rotary switch, which is of interest within the scope of the present invention. State of the art

[0003] German patent DE 103 58 032 A1 discloses an electric hand tool of the type of interest here, which includes several operating modes, namely impact drilling, drilling and chiseling / hammering, which can be set via a manually operated rotary selector switch from the outside, wherein a motor control for an electric motor as a drive unit is provided, whereby in at least one first operating mode, the electric motor is actively braked with a first run-down time, wherein in at least one second operating mode, the electric motor is braked with a second run-down time, different from the first, in order to ensure mode-appropriate operating behavior of the electric hand tool.

[0004] According to the generally known prior art, such a conventional transmission shifting mechanism, actuated via a manual rotary selector switch, comprises various transmission elements arranged along a chain of action, in particular a shift rod whose angle is adjustable by the rotary selector switch and which has a shift cam defining the different shift positions. A stationary detent spring acts on this cam. The shift rod, which can be detented and thus its angle is adjustable, acts on a shift plunger or the like to convert the shift position defined by the arrangement of the actuating cams of the shift rod into a translational movement, thereby axially actuating a clutch sleeve for mode selection.

[0005] A disadvantage of previously known gear-shifting mechanisms of the type of interest here is often the direct coupling of the rotary selector switch to the subsequent gear components that are moved by it. During switching, intermediate positions between two defined switching positions can occur, which can lead to a damaging collision of moving gear parts in the power tool. In the long term, this can result in significant wear and tear, potentially leading to failure of the power tool.

[0006] It is therefore the object of the present invention to further improve a transmission shifting mechanism of the type described above in such a way that undesirable intermediate positions between defined shift positions are avoided by simple technical means when selecting the operating mode. Disclosure of the invention

[0007] The problem is solved starting from a gear-shifting mechanism according to the preamble of claim 1 in conjunction with its characterizing features. The following dependent claims specify advantageous embodiments of the invention. Dependent claim 12 relates to an electric hand tool, in particular a rotary hammer, which is equipped with a gear-shifting mechanism according to the invention.

[0008] The invention includes the technical teaching that, in order to avoid undefined intermediate positions when switching between different operating modes, the spring means cooperating with the transmission means are designed as a combined spring arrangement, which comprises at least one first spring element of a first spring type, which is arranged in the chain of action between the rotary selector switch and the shift rod, and at least one second spring element of a second spring type, which cooperates with the shift gate of the shift rod to lock the selected switching position.

[0009] The advantage of the solution according to the invention lies in the fact that the combined spring arrangement of at least two different spring types results in a specific switching characteristic described below when switching between two operating modes, thereby avoiding undefined intermediate positions during switching. While the first spring type, preferably a curved spring, ensures that the rotary selector switch is no longer directly rotationally coupled to the switching rod, the second spring type, preferably a snap spring, acts primarily as a locking mechanism for the switching mechanism.

[0010] Preferably, the first spring element, in the form of a curved spring, is attached to the end face of the shift rod and interacts with an elastic deflection section with drive lugs molded onto the rear of the rotary selector switch to provide a spring-loaded rotary coupling with the shift rod. The rotary selector switch is also secured against loss in its axial position on the transmission shift mechanism via the design of the drive lugs, in a functionally integrated manner. However, the retention device can be removed in a defined position of the rotary selector switch. This eliminates the need for additional fasteners to secure the rotary selector switch.

[0011] According to a preferred embodiment, the first spring element is arranged on the shift rod such that a rotation of the rotary selector switch acting on the first spring element leads to a proportional increase in torque beyond a preload torque. In contrast to a direct coupling, this results in a gradual increase in the actuating torque, so that not every angular adjustment of the rotary selector switch leads to an immediate rotation of the shift rod and thus to a gradual release of the locking mechanism of the shift gate effected by the second spring element. This means that a slight rotation of the rotary selector switch cannot move the shift rod into an undefined intermediate position.

[0012] Preferably, the spring-loaded rotation angle between the rotary selector switch and the switching rod is limited by end stops on both sides. This ensures that the gradual increase in torque results in a direct mechanical coupling of the rotary selector switch with the switching rod, which, upon reaching the end stop, continues to rotate by the same angle, so that the previous switching position is no longer affected.

[0013] In other words, the second spring element can be moved out of its engaged position within the range of the progressive, end-stop-coupled rotation angle of the shift rod. The second spring element, now disengaged, is then engaged in the next position of the shift gate due to the preload torque of the first spring element.

[0014] According to a preferred embodiment, which ensures a haptically optimal relationship between the rotation of the rotary selector switch and the resulting change in the switching position, the initial spring-loaded rotation angle is selected in the range of 10° to 25°, preferably 17.5°, and the subsequent end-stop-coupled rotation angle is selected in the range of 20° to 50°, preferably 25°, before the switching cam of the switch rod slides into the next switching position under the action of the second spring element. This preferably occurs via a rotation angle of 12.5°. Overall, this results in the operating mode being switched via a rotation angle of 55° of both the rotary selector switch and the switch rod.

[0015] According to a preferred embodiment, it is provided that, in order to perform the switching operation with the second spring element engaged, the switching rod takes over the switching, so that the switching rod reaches the next switching position at the same time as the rotary selector switch. Detailed description based on drawing

[0016] Further measures improving the invention are described in more detail below, together with a description of a preferred embodiment of the invention, with reference to the figures. The figures show: Fig. 1 a first perspective view of a gear shifting mechanism for selecting between different operating modes, Fig. 2 a second perspective view of the gear shifting mechanism after Fig. 1 , Fig. 3 a graphic representation of a change of the switching position by changing the angle of rotation in connection with the resulting actuating torque, Fig. 4 a perspective view of the switching rod with the second spring element in the assembly position, and Fig. 5 a perspective view of the switching rod with the second spring element in the first switching position.

[0017] According to Fig. 1 A gear-shifting mechanism for selecting between different operating modes in an electric hand tool (not shown here) consists of a manually operated rotary selector switch 1 for adjusting the angle of a shift rod 2, which is equipped with a shift gate 3 to exert an axial actuating force on a clutch sleeve 5 in conjunction with the short arm of a shift lever 4 to select the operating mode. The actuating torque is transmitted from the rotary selector switch 1 to the shift rod 2 via a first spring element 6 designed as an arc spring. Furthermore, a stop 8 is integrally formed on the rotary selector switch 1 as an end stop for the shift rod 2, enabling direct transmission of the actuating force at the end of the spring travel of the first spring element 6.

[0018] A coupling sleeve 9, located adjacent to the shift rod 2, serves to positively engage another output shaft (not shown) with a gear (not shown) mounted on a shaft below the coupling sleeve 9. The coupling sleeve 9 is rotationally fixed but axially displaceable from the output shaft by its internal teeth. In the engaged state, the coupling sleeve 9 is pressed downwards by a spring (not shown). This causes the claws of the coupling sleeve 9 to engage with recesses on the gear, and the shaft rotates with the gear. In another switching position of the shift rod 2, another switching cam on the shift rod 2 lifts the coupling sleeve 9 upwards against the spring force. This disengages the claws from the gear, and the output shaft comes to a standstill.

[0019] As from Fig. 2 As can be seen more clearly, a pair of second spring elements 7a and 7b designed as snap springs, in conjunction with the shift gate 3, serve to lock the shift rod 2 in the selected shift position.

[0020] By attaching the first spring element 6 to the switching rod 2, the first spring element 6, designed as a bow spring, is pre-tensioned. Subsequent insertion of the rotary selector switch 1 establishes a connection between the rotary selector switch 1 and the switching rod 2 via the first spring element 6. The rotary selector switch 1 can only be mounted in one position and is axially secured by the first spring element 6. When the user turns the rotary selector switch 1 – in either direction – the first spring element 6 is wound up, thus increasing the torque acting on the switching rod 2. Both the rotary selector switch 1 and the switching rod 2 have the aforementioned stop lugs 8, which permit only a defined relative angle of rotation of the rotary selector switch 1 with respect to the switching rod 2.When the angle / position is reached where the surfaces of the stop lugs 8 touch, a direct coupling is created between the rotary selector switch 1 and the switching rod 2. As a result, the torque applied by the user is transferred directly to the switching rod 2 and the first spring element 6 is protected from overload.

[0021] According to Fig. 3 The change between switching positions is achieved via a rotation angle α of 55° of the rotary selector switch 1 and the spring-coupled switching rod 2. The actuating torque M of the rotary selector switch 1 acts on the first spring element via an initial rotation angle α of 17.5°, so that the actuating force increases proportionally up to position a. Once the rotary selector switch 1 has reached its end stop, the switching rod 2 is positively driven from position b onwards. This is maintained until a rotation angle of 42.5° is reached, before the second spring element engages in the next detent position for the following switching position due to the applied spring force, which generates a corresponding preload torque for the switching rod 2.To perform the switching operation with the second spring element 7 engaged, the switching rod 2 takes over the switching, so that the switching rod reaches the next switching position at the same time as the rotary selector switch 1.

[0022] The Fig. 4 Illustrates the assembly position of the shift rod 2, in which an axially aligned detent position is provided for the pair of second spring elements 7a and 7b.

[0023] During a Fig. 5 The depicted counterclockwise rotation of the switching rod 2 eliminates the alignment, so that the associated edge flanges 10a and 10b of the switching rod 2, in conjunction with the spring elements 7a and 7b, form an axial locking device.

[0024] To prevent the switching rod 2 from rotating beyond the four switching positions implemented here, additional radially outward-pointing stop lugs 8a and 8b are integrally formed on the switching rod 2, which interact with the housing of the power tool (not shown here). This ensures that only the intended four switching positions, each with a 55° angle, can be executed.

[0025] The invention is not limited to the preferred embodiment described above. Variations thereof are also possible and are covered by the scope of protection of the following claims. For example, it is also conceivable to design the first and second spring elements as a different type of spring and to implement them in a multiple arrangement connected in parallel within the transmission shifting mechanism. Reference symbol list

[0026] 1 Selector switch 2 Shift rod 3 Shift gate 4 Shift rocker 5 Coupling sleeve 6 First spring element 7 Second spring element 8 Stop bar 9 Coupling sleeve 10 Edge collar Actuating torque α Angle of twist

Claims

1. Gear shift mechanism for selecting between different operating modes in an electric hand tool, comprising a manually operable rotary selector switch (1) for adjusting the angle of a shift rod (2) provided with a shift cam (3), which acts on subsequent gear elements via molded actuating cams to set a desired operating mode, wherein cooperating spring elements are provided for locking the shift rod (2) in the selected shift position, characterized by the fact that the spring means are designed as a combined spring arrangement, comprising at least a first spring element (6) of a first spring type, which is arranged in the operative chain between the rotary selector switch (1) and the switching rod (2), and at least a second spring element (7) of a second spring type, which cooperates with the switching cam (3) of the switching rod (2) in corresponding detent positions to lock a selected switching position.

2. Gear shifting mechanism according to claim 1, characterized by the fact that the first spring element (6) is designed in the manner of a bow spring.

3. Gear shifting mechanism according to claim 1 or 2, characterized by the fact that the second spring element (7) is designed in the manner of a snap spring.

4. Gear shifting mechanism according to one of the preceding claims, characterized by the fact that The transmission means following the shift rod (2) include a pivoting shift rocker (4) which actuates a clutch sleeve (5) for setting the operating mode.

5. Gear shifting mechanism according to one of the preceding claims, characterized by the fact that the rotary selector switch (1) is fixed in its axial position by the first spring element (6).

6. Gear shifting mechanism according to one of the preceding claims, characterized by the fact thatthe first spring element (6) is arranged on the switching rod (2) such that a rotation of the rotary selector switch (1) acting on the first spring element (6) leads to a proportional increase of the torque beyond a preload torque.

7. Gear shifting mechanism according to claim 6, characterized by the fact that The spring-loaded rotation angle between the selection rotary switch (1) and the switching rod (2) is limited by end stops on both sides.

8. Gear shifting mechanism according to claim 7, characterized by the fact that the spring-loaded rotation angle is between 10° and 25° and the subsequent end-stop-coupled rotation angle is between 20° and 50°.

9. Gear shifting mechanism according to claim 7 or 8, characterized by the fact that In the rotation range of the end-stop-coupled rotation angle of the shift rod (2), the second spring element (7) can be moved from its locked position on the shift gate (3) in order to be transferred to the next shift position.

10. Gear shifting mechanism according to claim 9, characterized by the fact that The second spring element (7), which is disengaged for switching, is engaged in the next switching position of the shift gate due to the preload torque of the first spring element.

11. Gear shifting mechanism according to one of the preceding claims, characterized by the fact that To perform the switching operation with the second spring element (7) engaged, the switching rod (2) takes over the switching operation, so that the switching rod reaches the next switching position at the same time as the rotary selector switch (1).

12. Electric hand tool, in particular a rotary hammer, comprising a gear switching mechanism for selecting between different operating modes according to one of the preceding claims.

Images