Reciprocating saw

Description

[0001] The present invention relates to a reciprocating saw comprising a motion converter for converting a rotary movement of the output shaft of a drive motor. State of the art

[0002] Hand tools, especially reciprocating saws of the type described above, are well known and, depending on the selection and quality of the saw blade, are used for cutting various objects made of a variety of materials, such as metal, wood, or plaster. The availability of cordless, battery-powered versions allows such reciprocating saws to be used in confined spaces or at unusual angles, such as those required when installing heating, ventilation, and air conditioning pipes or electrical wiring.

[0003] Reciprocating saws are often powered by a drive motor and a motion converter to convert the rotary motion of the drive motor's output shaft into a reciprocating motion to move the saw blade back and forth. Various approaches have been developed for this purpose. Common variants of these motion conversion devices include, for example, grinding cranks, slider-crank mechanisms, eccentric drives, or.

[0004] In a typical swashplate drive, for example, the drive arm of a primary swashplate has a spherical tip that engages a matching hole in the spindle, which is then driven back and forth.

[0005] An eccentric drive is disclosed, for example, in EP2842675A1. The drive is provided by a drive motor that drives an eccentric via a gear. A connecting rod runs on this eccentric, which converts the rotary motion of the drive motor into a thrust motion of the connected saw blade via a second connecting rod. To suppress vibrations, this document further discloses a counterweight device for use in a reciprocating saw, comprising a drive, a lifting rod, and at least one first articulated rod.

[0006] The disadvantage of the handheld power tools known from the prior art, particularly reciprocating saws, for example, EP2842675A1 or US2705980A, is that, due to their design, they often have a considerable weight, which makes them unsuitable for easy handling in confined spaces. Furthermore, the design of the motion converter in the prior art is usually complicated, not very robust, and / or costly. Such motion converters are known for various applications, for example, from US5077902A, US2330618A, or US1948109A. Disclosure of the invention

[0007] It is an object of the invention to improve the above-mentioned disadvantages and to provide a reciprocating saw comprising a motion converter for converting a rotary motion of the output shaft of a drive motor, by means of which the working performance is increased, and wherein a simple, effective, cost-effective and / or energy-efficient conversion of a rotary motion into a lifting motion can be provided.

[0008] This object is achieved by a reciprocating saw according to claim 1, comprising a motion converter for converting a rotary motion of the output shaft of a drive motor. Advantageous embodiments, variants, and further developments of the invention can be found in the subclaims.

[0009] A reciprocating saw according to the invention comprises a housing, a drive motor with an output shaft, a spindle for receiving a tool, in particular a saw blade, and a motion converter for converting a rotary motion of the output shaft into a reciprocating motion of the spindle. The motion converter comprises an eccentric element driven by the output shaft for rotation about a rotational axis, with a driver part arranged eccentrically to the rotational axis, and a pendulum element pivotally mounted about a bearing point and connected to the spindle via a coupling point.

[0010] According to the invention, the pendulum element has a guide element for guiding the driver part. The guide element is arranged between the bearing point and the coupling point.

[0011] According to the invention, the bearing point and the coupling point further define a first axis of the pendulum element; wherein the guide element allows a movement component of the driver part relative to the pendulum element directed along the first axis of the pendulum element and largely prevents a movement component of the driver part relative to the pendulum element directed perpendicular to the first axis of the pendulum element.

[0012] Furthermore, the pendulum element has a guide element between the first end and the second end for guiding the driver part. According to the invention, the guide element allows a movement component of the driver part relative to the pendulum element directed along the longitudinal axis of the pendulum element and largely prevents a movement component of the driver part relative to the pendulum element directed perpendicular to the longitudinal axis of the pendulum element.

[0013] The pendulum element has a first end and a second end, wherein the first end is advantageously mounted within the housing via the bearing point and the second end is connected to the spindle via the coupling point.

[0014] In a preferred embodiment, the first end and the second end define a longitudinal axis of the pendulum element.

[0015] Advantageously, the spindle is at least partially mounted in the housing, wherein the rotary movement of the output shaft is converted into a reciprocating movement of the spindle relative to the housing. In this way, an effective and progressive cutting performance of the reciprocating saw can be achieved, wherein it is a relatively simple and robust design that is cost-effective to manufacture. The kinematics according to the invention, which is achieved by the arrangement of the pendulum element in conjunction with the driver part and the spindle, also ensures that the spindle has different speeds during the forward and backward movement, which enables fast and energy-efficient sawing progress.

[0016] In a particularly advantageous embodiment, the guide element forms a receptacle in the pendulum element, into which the driver part engages. This design, in turn, is characterized by its high robustness.

[0017] It can be provided that the receptacle forms an elongated hole, wherein the elongated hole is aligned along the longitudinal axis of the pendulum element.

[0018] Advantageously, the eccentric element is an eccentric disc, the driver part being a cylinder arranged on the eccentric element.

[0019] Furthermore, it is advantageous if the driver part is mounted in the guide element with a ring bearing. This reduces friction between the driver part and the guide element, which in turn has the beneficial effect of reducing wear on the parts and ensuring smoother running.

[0020] In a preferred embodiment, a first distance of the guide element from the bearing point and a second distance of the coupling point from the bearing point are coordinated with one another in such a way that the back and forth movement of the pendulum element has a first amplitude at the guide element and a second amplitude at the coupling point, wherein an amplitude ratio of the second amplitude to the first amplitude has a value not equal to 1.

[0021] Advantageously, the amplitude ratio (R) has a value R>1, in particular a value R>1.5, particularly preferably a value R>2.

[0022] In an advantageous embodiment, the bearing point has at least a distance Δ perpendicular to a longitudinal axis of the spindle in each position of the spindle, wherein the distance Δ has a fixed value greater than zero.

[0023] Advantageously, the axis of rotation is perpendicular to the output shaft and the eccentric element is driven by the output shaft via a worm drive.

[0024] Preferably, the spindle is mounted on the housing by means of a needle bearing. This allows the kinematics of the spindle movement to be influenced, in particular, the movement of the spindle and ultimately the saw blade can be controlled along an arcuate path.

[0025] In a further embodiment, the needle bearing prevents a movement component of the spindle relative to the housing that is directed transversely to a longitudinal axis of the spindle.

[0026] Advantageously, a third distance between the needle bearing and the coupling point along the first axis of the spindle is selected such that the reciprocating motion of the spindle is superimposed by a tilting motion of the longitudinal axis of the spindle around the needle bearing, resulting in an orbital motion of the tool at the tip of the tool. This orbital motion results in a fast and highly efficient sawing process with high cutting performance.

[0027] Advantageously, an eccentric counterweight is mounted on the driver part to compensate for any imbalance of the eccentric element. This allows the reciprocating saw to operate with particularly low vibration.

[0028] It has proven to be an advantage that the reciprocating saw is a corded reciprocating saw equipped with an electric drive motor, or a cordless reciprocating saw equipped with a battery-powered electric drive motor or an internal combustion drive motor.

[0029] Further features, possible applications, and advantages of the invention will become apparent from the following description of the exemplary embodiments of the invention, which are illustrated in the drawings. It should be noted that the features described or illustrated in the figures, either individually or in any combination, are merely descriptive of the subject matter of the invention, regardless of their summary in the patent claims or their reference, as well as regardless of their wording or representation in the description or drawings, and are not intended to limit the invention in any way. Drawings

[0030] The invention is explained in more detail below with reference to exemplary embodiments illustrated in the drawings. They show: Fig. 1 is a schematic side view of a reciprocating saw according to the invention with a motion converter; Fig. 2 is a schematic side view of the motion converter from Figure 1 in section A; Fig. 3 a first schematic perspective side view of the motion converter from Figure 1 in section A; Fig. 4 a second schematic perspective side view of the motion converter from Figure 1 in section A; and Fig. 5 a schematic partial section of the motion converter from Fig. 1 ; Fig. 6 a schematic representation of the kinematics of the motion converter in a reciprocating saw; Fig. 7 a trajectory of a tip of a tool in connection with the Figure 6 illustrated kinematics; and Fig. 8 a schematic representation of a speed curve of a tip of a tool mounted on a reciprocating saw according to the invention.

[0031] The Figure 1shows a side view of a battery-operated reciprocating saw 100 according to the invention, which is designed as a reciprocating saw 100 by way of example. Figure 2 shows some of the components arranged within a housing 110 of the hand-held power tool.

[0032] These components include, among others, an electric drive motor 200 with output shaft 210 and a spindle 112, at least partially mounted in the housing 110, for receiving a tool 114. In the embodiment shown, the spindle 112 protrudes from the housing 112 in the region of a workpiece stop 116. Furthermore, a motion converter 500 is arranged within the hand-held power tool 100 for converting a rotary movement of the output shaft 210 into a reciprocating movement of the spindle 112 relative to the housing 110. The spindle 112 is thus movably attached to the housing 110 and drivingly coupled to the electric drive motor 200. The tool 114, which is designed, for example, as a saw blade as shown, is attached to a first end of the spindle 112. The second end of the spindle 112 is located in the embodiment shown in any position within the housing 110 and is connected to a Figures 2 to 5described in more detail pendulum element 400.

[0033] The housing 110 has a first handle 117, which has the shape of a closed bracket and forms an opening 115 so that a user can better grip the handle 117 with their fingers. Furthermore, the housing 110 has a battery pack 600 and, in the upper area of ​​the handle 117, an operating element 119 for controlling the drive motor.

[0034] As in the Figures 2 to 5 Shown in detail, a motion converter 500 has an eccentric element 300 driven by the output shaft 210 in rotation about a rotation axis 220 with a driver part 310 arranged eccentrically to the rotation axis 220.

[0035] Furthermore, the motion converter 500 has a pendulum element 400 with a first end 410 and a second end 420. The first end 410 is pivotally mounted within the housing 110 at a bearing point P and the second end 420 is connected to the spindle 112. In this way, the pendulum element 400 can execute a pendulum or rocking movement about the bearing point P. The spindle 112 is mounted by means of a needle bearing 118 in a Figure 6 shown point D on the housing 110, so that at this point D a movement component of the spindle 112 directed transversely to a longitudinal axis of the spindle 112 relative to the housing 110 is prevented. The bearing point P in every position of the spindle 112 is at least a distance Δ>0 perpendicular to a longitudinal axis of the spindle 112.

[0036] As in the Figure 3 and 4As can be seen, the rotational axis 220 in the embodiment shown is perpendicular to the output shaft 210. The eccentric element 300 is therefore driven in this embodiment via a worm drive from the output shaft 210, wherein in the embodiment shown a worm wheel 211 is located on the output shaft, which in Figure 5 is shown.

[0037] The first end 410 and the second end 420 of the pendulum element define a longitudinal axis L of the pendulum element 400, wherein the pendulum element 400 has a guide element 430 between the first end 410 and the second end 420.

[0038] In the illustrated embodiment, the guide element 430 has an elliptical receptacle which engages with a driver part 310 of the eccentric element 300 arranged eccentrically to the rotation axis 220.

[0039] In the embodiment shown, the eccentric element 300 is an eccentric disc that supports the driver part 310, which is designed as a cylinder. To reduce friction between the driver part 310 and the guide element 430, a ring bearing 314 is arranged between the two components.

[0040] To reduce vibrations during operation, an eccentric counterweight 312 is arranged on the driver part 310 to compensate for the imbalance of the eccentric element 300.

[0041] Figure 6shows a schematic representation of the kinematics of the motion converter 500. The pendulum element 400 is represented by its longitudinal axis L in the different positions L', L" and L‴. Due to the mounting of the first end 410 at the bearing point P, the representations L', L" and L‴ of the longitudinal axis L intersect at point P. The second end 420 of the pendulum element 400 is connected to the spindle 112, which in turn is mounted transversely on the housing at point D via the needle bearing 114.

[0042] The path of a center point of the driver part 310 is in Figure 6 represented by the circle A. Since in the embodiment shown the center of the driver part 310 always lies on the longitudinal axis L of the pendulum element 400, a position of the center of the driver part 310 at A1 corresponds to a position of the longitudinal axis at L'. Figure 6This is the position at which the spindle 112 is maximally retracted into the housing. Accordingly, a position of the center of the driver part 310 at A2 corresponds to a position of the longitudinal axis at L‴. This, in turn, is the position at which the spindle 112 protrudes maximally from the housing. A1 and A2 correspond to the reversal points of the spindle 112 in its stroke movement along its longitudinal axis.

[0043] When the center point of the driver part 310 rotates clockwise along the circular path A, represented by the arrow R, the distance between this center point and the bearing point P increases and decreases cyclically. This distance has the maximum value d3 at point A3 and the minimum value d4 at point A4. At a constant rotational speed of the drive motor 200, this means that the pendulum movement of the pendulum element 400 from the position L‴ to L' is faster than that from the position L' to L‴. This can be referred to as an asymmetric cutting movement. Accordingly, the lifting movement of the spindle 112 in the direction into the housing 112 is faster than the opposite movement out of the housing 112. When the teeth on the saw blade 114 are arranged such that they cut in tension, i.e. when the spindle moves in the direction into the housing, this means that the cutting movement is carried out with greater energy than the lifting movement out of the housing.This ensures a high level of efficiency in the cutting process.

[0044] It is Figure 6 It can also be seen that the kinematics results in a tilting of the longitudinal axis of the spindle 112 around the needle-bearing point D, which overlays the lifting movement of the spindle 112. This leads to a point E at the end of the spindle 112 remote from the pendulum element 400 performing a movement along the path 600, which in Figure 7 is shown enlarged. This type of movement, which is also transmitted to the saw blade 114, can be described as orbital movement and results in a fast and highly efficient sawing process with high cutting performance.

[0045] The Figure 6 The relationships explained are shown again in Figure 8 clarified. Figure 8 shows a diagram showing the magnitude of the orbital speed at Figure 6represented point E over the angle swept by the pendulum element 400 (as a sum in terms of amount) in the form of a curve v.

[0046] Due to the reciprocating motion of spindle 112, curve v has a cyclical profile. Since the path velocity of point E is ultimately due to the circular motion of driver part 310, which is transmitted via a variable lever arm to pendulum element 400 and thus to spindle 112, curve v has a profile in sections that can be described as approximately sinusoidal.

[0047] The Figure 8 The points A1, A2, A3, and A4 on the curve v correspond to the points in Figure 6 illustrated positions of the driver part 310 along the circle A. According to the context of the Figure 6According to the kinematics described, the path speed of point E, which is also transferred to, for example, a saw blade, is maximum at point A4, i.e. at the maximum movement of the spindle 400 directed towards the housing, while it is minimum at points A1 and A2, i.e. the reversal points of the spindle 112, corresponding to the positions L' and L‴ of the pendulum element 400. At point A3, corresponding to the maximum speed of the spindle 112 directed out of the housing, the curve v reaches a value which, in the present embodiment of the invention, is 42% below the value reached at point A4.

[0048] In addition to the embodiments described and illustrated, further embodiments are conceivable, which may include further modifications and combinations of features.

Claims

1. Reciprocating saw (100) comprising a housing (110), a drive motor (200) with an output shaft (210), a spindle (112) for receiving and driving a tool (113), in particular a saw blade, and a motion converter for converting a rotational movement of the output shaft (210) into a reciprocating movement of the spindle (112); wherein the motion converter comprises an eccentric element (300) which is driven by the output shaft (210) so as to rotate about a rotation axis (220) and has an entrainment part (310) disposed eccentrically to the rotation axis (220), and an oscillating element (400) which is mounted so as to be pivotable about a bearing point (P) and by way of a coupling point (114) is connected to the spindle (112); wherein the oscillating element (400) has a guide element (430) for guiding the entrainment part(310); wherein the guide element (430) is disposed between the bearing point (P) and the coupling point (114), characterized in that the bearing point (P) and the coupling point (114) define a first axis of the oscillating element (400); wherein the guide element (430) permits a movement component of the entrainment part (310) directed along the first axis of the oscillating element (400) relative to the oscillating element (400), and largely prevents a movement component of the entrainment part (310) directed perpendicularly to the first axis of the oscillating element (400) relative to the oscillating element (400).

2. Reciprocating saw (100) according to Claim 1, characterized in that the guide element (430) forms a receptacle in the oscillating element (400) in which the entrainment part (310) engages.

3. Reciprocating saw (100) according to one of the preceding claims, characterized in that the receptacle is a slotted hole, wherein the slotted hole is substantially aligned along the first axis of the oscillating element (400).

4. Reciprocating saw (100) according to one of the preceding claims, characterized in that a first spacing (e1) of the guide element (430) from the bearing point (P) and a second spacing (e2) of the coupling point (114) from the bearing point (P) are mutually adapted in such a manner, that the reciprocating movement of the oscillating element (400) on the guide element (430) has a first amplitude (Amp1) and on the coupling point (114) has a second amplitude (Amp2), wherein an amplitude ratio (R) of the second amplitude (Amp2) to the first amplitude (Amp1) has a value not equal to 1.

5. Reciprocating saw (100) according to Claim 4, characterized in that the amplitude ratio (R) has a value R>1, in particular a value R>1.5, particularly preferably a value R>2.

6. Reciprocating saw (100) according to one of the preceding claims, characterized in that the bearing point (P) in each position of the spindle (112) has at least a spacing Δ perpendicular to a longitudinal axis of the spindle (112), wherein the spacing Δ has a fixed value greater than zero.

7. Reciprocating saw (100) according to one of the preceding claims, characterized in that the rotation axis (220) is perpendicular to the output shaft, and wherein the eccentric element (300) is driven by the output shaft (210) by way of a worm drive.

8. Reciprocating saw (100) according to one of the preceding claims, characterized in that the spindle (112) by means of a needle bearing (118) is mounted on the housing (110), wherein the needle bearing (118) prevents a movement component of the spindle (112), which is directed transversely to a longitudinal axis of the spindle (112), relative to the housing (110).

9. Reciprocating saw (100) according to one of Claims 4 and 8, characterized in that a third spacing (e3) between the needle bearing and the coupling point (P) along the longitudinal axis of the spindle (112) is chosen in such a way, that the reciprocating movement of the spindle (112) is superimposed by a tilting movement of the longitudinal axis of the spindle (112) about the needle bearing, so that an orbital movement of the tool (113) at the tip (115) of the tool (113) is established.

10. Reciprocating saw (100) according to one of the preceding claims, characterized in that an eccentric counterweight (312) is disposed on the entrainment part (310) to compensate for an imbalance of the eccentric element (300).