JIANG, Xianbin (No.82 Laijiali Xinsheng, Binjiang DistrictHangzhou City, Zhejiang 2, 310052, CN)
WIKER, Juergen (No. 567 Bin Kang Road, Binjiang DistrictHangzhou City, Zhejiang 2, 310052, CN)
ZHOU, Peng (No.83 Wenyi West Road, Xihu Distric, Hangzhou City Zhejiang 1, 310011, CN)
JIANG, Xianbin (No.82 Laijiali Xinsheng, Binjiang DistrictHangzhou City, Zhejiang 2, 310052, CN)
WIKER, Juergen (No. 567 Bin Kang Road, Binjiang DistrictHangzhou City, Zhejiang 2, 310052, CN)
| Cl aims 1. Protective device for a machine tool (12a), in particular a circular saw, with a protective hood (14a-k) which can be moved between at least one working position and a protecting position, characterized by a return-momentum reducing unit (16a-k), which is provided for the purpose of at least partially reducing rebound of the protective hood (14a-k) when the protecting position is reached. 2. Protective device according to Claim 1, characterized in that the return-momentum reducing unit (16a-d; 16g; 16h; 16k) is provided for the purpose of slowing down the protective hood (14a-d; 14g; 14h; 14k) before the protecting position is reached during movement from the working position into the protecting position. 3. Protective device according to Claim 2, characterized in that the return-momentum reducing unit (16k) has an air damping unit (21k), which is provided for the purpose of slowing down the protective hood (14k) . 4. Protective device according to one of the preceding claims, characterized in that the return-momentum reducing unit (16a-k) is intended for the purpose of absorption of kinetic energy of the protective hood (14a-k) . 5. Protective device according to one of the preceding claims, characterized in that the protective hood (14a-k) has an edge region (20a-k) facing in a direction of movement (18a-k) from the working position into the protecting position and the return-momentum reducing unit (16a-k) is at least partially arranged in the edge region (20a-k) . 6. Protective device according to one of the preceding claims, characterized in that the return-momentum reducing unit (16a-k) has a capturing unit (22a-k) , which is provided for the purpose of capturing the protective hood (14a-k) during movement from the working position into the protecting position. 7. Protective device according to Claim 6, characterized in that the capturing unit (22a-k) has at least one capturing element (24a-k; 26e-j; 28g; 28h) , which is arranged on the protective hood (14a-k) . 8. Protective device at least according to Claim 7, characterized in that at least one of the capturing elements (24a-k; 26e-j; 28g; 28h) is formed at least partially in one piece with the protective hood (14a-k) . 9. Protective device at least according to Claim 6, characterized in that the capturing unit (22a-k) has at least one capturing element (30a-k) , which is arranged on a housing (34a-k) and/or a guiding unit (36a-k) of the machine tool (12a) . 10. Protective device according to Claim 9, characterized in that the capturing element (3Oe; 3Of) is mounted at least partially movably on the housing (34e; 34f) and/or the guiding unit (36e; 36f) . 11. Protective device at least according to Claim 7 and/or 9, characterized in that at least one of the capturing elements (24a; 30b; 30c; 24d-k; 30k) is at least partially formed by a recess (38a; 40b; 40c; 38d-k; 40k) . 12. Protective device at least according to Claim 7 and/or 9, characterized in that least one of the capturing elements (24a; 30b) is at least partially formed by a tapered recess (38a; 40b) . 13. Protective device at least according to Claim 7 and/or 9, characterized in that at least one of the capturing elements (30a-d; 3Og; 30k) is at least partially formed by a frictional element (42a-d; 42g; 42k; 44c) . 14. Protective device at least according to Claim 7 and/or 9, characterized in that at least one of the capturing elements (26i, 3Oi; 26j, 3Oj) is at least partially formed by a magnet (52i, 54i; 52j, 54j) . 15. Machine tool with a protective device (10a-k) according to one of the preceding claims. |
Prior art
The invention is based on a protective device according to the precharacterizing clause of Claim 1.
A protective device for a machine tool with a protective hood is known. The protective hood is in this case arranged such that it can be moved between a working position and a protecting position.
Advantages of the invention
The invention is based on a protective device for a machine tool, in particular a circular saw, with a protective hood which can be moved between at least one working position and a protecting position.
It is proposed that the protective device has a return- momentum reducing unit, which is provided for the purpose of at least partially reducing rebound of the protective hood when the protecting position is reached. In this connection, "provided" is to be understood in particular as meaning specially equipped and/or specially designed. The protective hood is advantageously arranged around a tool, in particular a rotating, disc-shaped tool, such as for example a circular saw blade, of the machine tool to protect the operator from undesired injuries, the protective hood preferably being arranged in a circumferential direction of the tool around a working region of the tool, such as for example a working edge and/or a sawing edge. Furthermore, "working position" is to be understood in particular as meaning a position of the protective hood that makes it possible for workpieces to be worked, such as in particular sawn, by a tool around which the protective hood is preferably arranged. In the working position of the protective hood, advantageously only a partial region of the tool is left uncovered by the protective hood, so that sawing of the workpiece can be made possible, the partial region extending to a region of the workpiece that is in contact with the workpiece while the rest of the tool is advantageously covered by the protective hood. After removal of a workpiece from the working edge and/or the sawing edge of the tool, the protective hood preferably moves of its own accord to the protecting position, such as for example on account of a resilient force of a spring. Furthermore, a "protecting position" is to be understood in particular as meaning a position of the protective hood in which the tool, in particular the working edge and/or the sawing edge of the tool, is covered by the protective hood, in particular covered almost completely, and consequently possible contact of the tool with an operator is prevented. Furthermore, a "return-momentum reducing unit" is to be understood in particular as meaning a unit that is provided for the purpose of reducing return momentum, which can be transferred to the protective hood, acting in a direction counter to a direction of movement extending from the working position into the protecting position, as a result of the protective hood colliding with a housing and/or some other component of the machine tool as a result of the law of conserving momentum. Transfer of the return momentum to the protective hood in the protecting position can be advantageously reduced by at least 50%, advantageously by at least 80%, preferably at least 95% and particularly preferably by 100%, by means of the return-momentum reducing unit . Reducing the return momentum can be advantageously achieved in this way by reducing momentum of the protective hood before the protecting position is reached, such as for example reducing the speed of movement of the protective hood, and/or by absorbing momentum transferred from the protective hood to the housing and/or other component when the protecting position is reached. The protective device according to the invention is designed to be used for preferably all machine tools that have a movably arranged protective hood. However, the protective device is particularly advantageously suitable for handheld circular saws on account of a high risk of a saw blade causing injury to an operator. The configuration according to the invention allows the protective hood in the protecting position to shield the operator and/or the workpiece from the tool, in particular the still rotating tool after completion of a sawing operation, and advantageously to prevent undesired exposure, in particular for a short time, of at least a partial region of the tool. This allows advantageous safety, in particular for an operator, to be achieved during operation and/or use of the machine tool, in that the operator and/or the workpiece can be shielded from possible contact with the tool and risk of injury to the operator can be advantageously prevented.
Furthermore, it is proposed that the return-momentum reducing unit is provided for the purpose of slowing down the protective hood before the protecting position is reached during movement from the working position into the protecting position. In this connection, "slowing down" is to be understood in particular as meaning reducing the speed of a component and/or an element, such as in particular the protective hood, counteracting force or negative acceleration preferably acting here on the moving component and/or element. It is advantageously possible in this way to reduce kinetic energy of the protective hood, and consequently at least reduce and/or prevent return momentum when the protective hood in the protecting position collides with another component, in particular a housing and/or a guiding unit of the machine tool, that can be transferred to the protective hood in the collision. A "guiding unit" is to be understood here in particular as meaning a unit of the machine tool that is provided for the purpose of guiding the machine tool on a workpiece to be worked, in particular during operation of the machine tool. The guiding unit preferably has a guiding and/or resting surface, with which the machine tool can rest on the workpiece to be worked.
It is further proposed that the return-momentum reducing unit has an air damping unit, which is provided for the purpose of slowing down the protective hood, whereby a particularly low cost and, in particular, weight-reducing return-momentum reducing unit can be achieved. Moreover, maintenance expenditure for the machine tool or the protective device can be minimized. In this connection, an "air damping unit" is to be understood in particular as meaning a unit that is provided for the purpose of reducing, in particular slowing and/or damping, the speed of the protective hood during movement from the working position into the protecting position, slowing down and/or damping of the speed of the protective hood taking place by means of a damping means formed by air, such as for example an air buffer and/or air cushion, whereby kinetic energy is preferably converted into internal energy of the air buffer and/or air cushion. The speed is preferably slowed down and/or reduced almost completely when the protecting position is reached, so that the protective hood in the protecting position comes substantially to a standstill and rebound of the protective hood is prevented almost completely.
It is also proposed that the return-momentum reducing unit is provided for the purpose of absorption of kinetic energy of the protective hood, whereby rebound of the protective hood in the protecting position can be advantageously prevented, at least partially, and consequently a particularly safe protective device that minimizes risk of injury to an operator of the machine tool can be achieved. "Absorption of kinetic energy" is to be understood here in particular as meaning acceptance and/or conversion by the return-momentum reducing unit of the kinetic energy of the protective hood, such as for example into thermal energy, frictional energy and/or other forms of energy that appear appropriate to a person skilled in the art.
A structurally simple and, in particular, space-saving arrangement of the return-momentum reducing unit can be achieved if the protective hood has an edge region facing in a direction of movement from the working position into the protecting position and the return- momentum reducing unit is at least partially arranged in the edge region. In this connection, an "edge region" is to be understood in particular as meaning a region of the protective hood that extends from an edge or an end of the protective hood into the protective hood in a circumferential direction of the protective hood counter to the direction of movement, the edge region covering a region of at most 30° and particularly advantageously a region of at most 20° in the circumferential direction.
It is further proposed that the return-momentum reducing unit has a capturing unit, which is provided for the purpose of capturing the protective hood during movement from the working position into the protecting position. A "capturing unit" is also to be understood in particular as meaning a unit that stops movement of the protective hood in at least one direction, in particular when the protecting position is reached, and also secures, in particular releasably secures, the protective hood in the protecting position, it preferably being possible for return momentum of the protective hood that would be transferred to the protective hood in a collision of the protective hood in the protecting position to be at least partially absorbed by the capturing unit. The capturing unit may in this case be formed by a form-fitting unit and/or a force-fitting unit and/or a firmly bonding unit. The configuration according to the invention advantageously allows prevention of rebound of the protective hood after the protecting position is reached, and consequently advantageously allows reduction of risk of injury to an operator.
In a further refinement of the invention, it is proposed that the capturing unit has at least one capturing element, which is arranged on the protective hood. This allows particularly advantageous matching of the capturing element to a component lying against the protective hood in the protecting position, such as in particular a housing and/or a guiding unit of the machine tool, to be achieved, and consequently allows securing, in particular releasable securing, of the protective hood in the protecting position by the capturing unit or by the capturing element to be achieved in a structurally simple way.
Furthermore, it is proposed that at least one of the capturing elements is formed at least partially in one piece with the protective hood, whereby further components, installation space, assembly effort and costs can be advantageously saved. In this connection, "in one piece" is to be understood in particular as meaning formed as one part and/or made in one casting operation and/or formed as one component.
It is proposed furthermore that the capturing unit has a capturing element which is arranged on a housing and/or a guiding unit of the machine tool, whereby the capturing unit can be realized in a structurally simple way. Moreover, this allows advantageous matching of a capturing element to the protective hood and of the capturing element to the housing and/or the guiding unit of the machine tool to be achieved. Moreover, it is also conceivable for the capturing element to be formed in one piece with the housing and/or the guiding unit .
Particularly simple and in particular releasable securing of the protective hood in the protecting position can be achieved if the capturing element is mounted at least partially movably on the housing and/or the guiding unit. The capturing element is preferably arranged such that it can be tilted about an axis and/or at least partially rotated. Particularly advantageously, the capturing element is at least partially formed by a catch, whereby structurally simple holding and/or securing of the protective hood in the protecting position can be achieved.
It is proposed furthermore that at least one of the capturing elements is at least partially formed by a recess, whereby a particularly space-saving and low- cost configuration of the capturing unit can be achieved. Moreover, this allows a corresponding capturing element to be received in a structurally simple way.
An advantageous slowing down effect, in particular of the protective hood, can be achieved if at least one of the capturing elements is at least partially formed by a tapered recess. A "tapered recess" is to be understood here in particular as meaning a recess that has a cross-sectional area which becomes smaller along a direction from an open end to a closed end of the recess. Furthermore, the recess or the tapered recess may also have a surface layer that assists the slowing down effect, such as in particular a surface layer that has a high friction coefficient.
It is also proposed that at least one of the capturing elements is at least partially formed by a frictional element, whereby the protective hood can be slowed down, or kinetic energy of the protective hood can be converted into frictional and/or thermal energy, and moreover the protective hood can be secured in the protecting position by static friction. In this connection, the "frictional element" is to be understood in particular as meaning an element that preferably has a surface layer with a high friction coefficient, in particular a higher friction coefficient than components surrounding the frictional element .
It is proposed furthermore that at least one of the capturing elements is at least partially formed by a latching element, whereby securing, in particular releasable securing, of the protective hood in the protecting position can be realized in a particularly simple way.
Furthermore, it is proposed that at least one of the capturing elements is at least partially formed by a magnet, whereby the protective hood can be advantageously held in the protecting position by means of a magnetic force, it being advantageously possible here for the magnetic force to counteract possible return momentum of the protective hood after a collision of the protective hood in the protecting position. Moreover, structurally simple release of the protective hood from the protecting position for renewed working of a workpiece can be achieved.
Drawing
Further advantages emerge from the following description of the drawing, in which exemplary embodiments of the invention are represented. The drawing, the description and the claims contain numerous features in combination. A person skilled in the art will expediently also consider the features individually and combine them in appropriate further combinations . In the drawing:
Figure 1 shows a handheld circular saw formed by a machine tool, with a protective device according to the invention, in a schematic representation,
Figure 2 shows a first variant of a return-momentum reducing unit, with a recess of a tapered form arranged on the protective hood, in a schematic representation,
Figure 3 shows a second variant of the return-momentum reducing unit, with a recess of a tapered form in a housing and/or a guiding unit, in a schematic representation,
Figure 4 shows a third variant of the return-momentum reducing unit, with a recess arranged on the housing and/or the guiding unit and having two frictional elements, in a schematic representation,
Figure 5 shows a fourth variant of the return-momentum reducing unit, with an inwardly widened recess arranged on the protective hood, in a schematic representation, Figure 6 shows a view of the detail of the recess of the protective hood from Figure 5,
Figure 7 shows a fifth variant of the return-momentum reducing unit, with a latching element rotatably arranged on the housing and/or the guiding unit, in a schematic representation,
Figure 8 shows a sixth variant of the return-momentum reducing unit, with an alternative configuration of the latching element in comparison with Figure 7, in a schematic representation,
Figure 9 shows a seventh variant of the return- momentum reducing unit, with a latching element arranged on the housing and/or the guiding unit, in a schematic representation, Figure 10 shows an eighth variant of the return- momentum reducing unit, with an alternatively formed latching element in comparison with Figure 9, in a schematic representation, Figure 11 shows a ninth variant of the return-momentum reducing unit, with capturing elements formed by magnets, in a schematic representation,
Figure 12 shows a tenth variant of the return-momentum reducing unit, with an alternative configuration of the magnets in comparison with Figure 11, in a schematic representation,
Figure 13 shows an eleventh variant of the return- momentum reducing unit, with an air chamber arranged in the protective hood, in a schematic representation,
Figure 14 shows the protective hood together with the housing and/or the guiding element from Figure 13 in a sectional representation and
Figure 15 shows the protective hood from Figure 13 in a view of a detail.
Description of the exemplary embodiments
In Figure 1, a machine tool 12a formed by a handheld circular saw 56a is represented. The handheld circular saw 56a comprises a housing 34a, a guiding unit 36a, which is provided for the purpose of guiding the handheld circular saw 56a on a workpiece, a protective device 10a and a disc-shaped circular saw blade 58a. The guiding unit 36a is arranged on an underside 60a of the housing 34a. The circular saw blade 58a extends through a principal plane of extent 62a of the guiding unit 36a, a partial region 64a of the circular saw blade 58a that is provided for the purpose of working, in particular sawing, being arranged on a side 66a of the guiding unit 36a that is turned away from the housing 34a. The protective device 10a comprises a first protective hood 68a, which is arranged such that it is fixed on the housing 34a and/or the guiding unit 36a, and a second protective hood 14a, which is arranged such that it can be moved between a working position and a protecting position. The two protective hoods 68a, 14a are arranged around a working edge 70a of the circular saw blade 58a that is formed by a sawing edge, in a circumferential direction 72a around the circular saw blade 58a. The first protective hood 68a is arranged here around a partial region 76a of the circular saw blade 58a that is arranged on a side 74a of the guiding unit 36a which is turned towards the housing 34a. The second protective hood 14a is arranged such that it can be moved around the circular saw blade 58a and, in a protecting position, is arranged around the partial region 64a that is arranged on the side 66a of the guiding unit 36a which is turned away from the housing 34a. In the protecting position
(represented by a solid line in Figure 1), the circular saw blade 58a is completely covered by the two protective hoods 14a, 68a, while in the working position (represented as a dash/double-dotted line in Figure 1) a partial region of the sawing edge of the circular saw blade 58a is exposed.
Furthermore, the protective device 10a has a return- momentum reducing unit 16a, which is provided for the purpose of at least partially preventing rebound of the second protective hood 14a when the protecting position is reached. For this purpose, the return-momentum reducing unit 16a is arranged partially on the housing 34a and/or the guiding unit 36a and/or the first protective hood 68a and partially on the second protective hood 14a. The second protective hood 14a has for this purpose an edge region 20a, which faces in a direction of movement 18a from the working position into the protecting position and in which the return- momentum reducing unit 16a is partially arranged.
In Figure 2, a first variant of the return-momentum reducing unit 16a of the protective device 10a from Figure 1 is represented. The return-momentum reducing unit 16a has for this purpose a capturing unit 22a, which is provided for the purpose of capturing the second protective hood 14a during a movement from the working position into the protecting position when the protecting position is reached. For this purpose, the capturing unit 22a has a capturing element 24a, which is formed by a recess 38a, is arranged on the second protective hood 14a and is formed in one piece with the latter. The recess 38a is formed by a tapered recess 38a. The capturing element 24a is arranged in the edge region 20a of the second protective hood 14a that faces in the direction of movement 18a from the working position into the protecting position, an opening 78a of the recess 38a facing in the direction of the direction of movement 18a.
Furthermore, the capturing unit 22a has a further capturing element 30a, which is arranged on the housing 34a and/or the guiding unit 36a. The capturing element 30a is formed in a cylindrical shape and is formed by a frictional element 42a. Along a radial direction 80a of the frictional element 42a, the frictional element 42a has in a centre 82a a fastening element 84a, by means of which the frictional element 42a is arranged on the housing 34a and/or the guiding unit 36a. Around the fastening element 84a up to an outwardly turned surface 86a along the radial direction 80a, the frictional element 42a is formed by an elastic material, such as for example a rubber, an elastomer, a PVC and/or further elastic materials that appear appropriate to a person skilled in the art.
If the second protective hood 14a moves from the working position into the protecting position after completion of a sawing operation, the second protective hood 14a is thereby slowed down by the return-momentum reducing unit 16a or the capturing unit 22a. As from first contact of the second protective hood 14a or the tapered recess 38a with the frictional element 42a, a static friction force thereby acts, counteracting movement of the second protective hood 14a from the working position into the protecting position. A surface 88a of the tapered recess 38a of the second protective hood 14a moves past the frictional element 42a, the static friction force acting between the surface 88a of the recess 38a and the frictional element 42a. On account of a static friction force acting between the frictional element 42a and the surface 88a of the recess 38a, kinetic energy of the second protective hood 14a is converted into frictional energy or thermal energy and thereby absorbed by the return-momentum reducing unit 16a. It may also be advantageous if the surface 88a of the recess 38a is formed by a frictional surface which can intensify a slowing down effect or energy absorption of the return- momentum reducing unit 16a.
If the second protective hood 14a is in the protecting position, it is held in the protecting position by the static friction force between the two capturing elements 24a, 30a of the capturing unit 22a or between the frictional element 42a and the surface 88a of the tapered recess 38a, so that rebounding of the second protective hood 14a of its own accord from the protecting position is prevented.
In Figures 3 to 15, alternative exemplary embodiments are represented. Components, features and functions that remain substantially the same are in principle numbered by the same reference numerals. However, to distinguish between the exemplary embodiments, the letters a to k are added to the reference numerals of the exemplary embodiments. The following description is substantially confined to the differences in comparison with the exemplary embodiment in Figures 1 and 2, it being possible to refer to the description of the exemplary embodiment in Figures 1 and 2 with respect to components, features and functions that remain the same.
In Figure 3, a second variant of a return-momentum reducing unit 16b of a protective device 10b is represented, provided for the purpose of at least partially preventing rebound of a second protective hood 14b when a protecting position is reached when moving from a working position into the protecting position. The return-momentum reducing unit 16b has a capturing unit 22b with a capturing element 24b, which is formed in one piece with the second protective hood 14b and is formed by a partial region 90b of an outwardly turned side 94b of a surface 92b of the second protective hood 14b that is turned away from a circular saw blade. Moreover, the capturing unit 22b has a further capturing element 30b, which is formed in a substantially cylindrical shape, in particular a dumbbell shape, with a tapered recess 40b running in the circumferential direction 96b of the capturing element 30b, formed by a groove and intended for receiving the second protective hood 14b in the protecting position. The recess 40b is arranged along a longitudinal extent 98 of the capturing element 30b in a central region 100b. The capturing element 30b is formed as a frictional element 42b of an elastic material, such as for example rubber, and is arranged on a housing and/or a guiding unit. In principle, it is also conceivable for the capturing element 30b to be formed at least partially in one piece with the housing and/or the guiding element. In a protecting position of the second protective hood 14b, surfaces 102b of the tapered recess 40b that lie opposite one another and are turned inwards lie against the surface 92b of the second protective hood 14b. During movement of the second protective hood 14b into the protecting position, the second protective hood 14b is slowed down, or kinetic energy of the second protective hood 14b is converted into frictional energy and/or thermal energy, by a static friction force which is directed counter to the movement of the second protective hood 14b and acts between the surface 92b of the second protective hood 14b and the surfaces 102b of the recess 40b. Furthermore, the second protective hood 14b is held in the protecting position by the static friction force.
In Figure 4, a third variant of a return-momentum reducing unit 16c of a protective device 10c is represented, provided for the purpose of at least partially preventing rebound of a second protective hood 14c when a protecting position is reached when moving from a working position into the protecting position. The capturing unit 22c of the return- momentum reducing unit 16c differs from the capturing unit 22b from Figure 3 to the extent that a capturing element 30c, which is arranged on a housing and/or a guiding unit, has a recess 40c running around the capturing element 30c in the circumferential direction 96c and two web-shaped frictional elements 42c, 44c. The frictional elements 42c, 44c are arranged on opposite walls 104c of the recess 40c, respectively on an edge region 106c of the wall 104c in the region of an opening 108c of the recess 40c, and thereby delimit an opening region 110c of the opening 108c. When the second protective hood 14c moves into the protecting position, the second protective hood 14c is guided past the two frictional elements 42c, 44c, the frictional elements 42c, 44c thereby being in contact with a surface 92c of the second protective hood 14c. Slowing down of the second protective hood 14c and securing in the protecting position by static friction force between the second protective hood 14c and the two frictional element 42c, 44c takes place in a way analogous to the description in relation to Figure 3.
In Figures 5 and 6, a fourth variant of a return- momentum reducing unit 16d of a protective device 1Od is represented, provided for the purpose of at least partially preventing rebound of a second protective hood 14d when a protecting position is reached when moving from a working position into the protecting position. A capturing unit 22d has a capturing element 3Od, which is formed by a frictional element 42d and is arranged on a housing and/or a guiding unit, the capturing element 3Od also being formed by a latching element 48d and being formed in a way analogous to the capturing element 30a in Figure 2. The capturing unit 22d has a further capturing element 24d, which is formed in one piece with the second protective hood 14d and is formed by a recess 38d. The recess 38d is formed as a latching element 46d and has an opening region 112d and a receiving region 114d for the frictional element 42d, the opening region 112d having a smaller cross-sectional area 116d than a cross- sectional area 118d of the receiving region 114d (Figure 6) . The cross-sectional area 12Od of the frictional element 42d is also larger than the cross- sectional area 116d of the opening region 112d and equal to or advantageously smaller than the cross- sectional area 118d of the receiving region 114d. When the second protective hood 14d moves into the protecting position, a latching connection between the two latching elements 46d, 48d, and consequently also between the second protective hood 14d and the housing and/or the guiding element, is achieved in the protecting position, so that rebounding of the second protective hood 14d is prevented. On account of the latching connection, the second protective hood 14d is also secured in the protecting position. Furthermore, kinetic energy of the second protective hood 14d is additionally converted into frictional energy or thermal energy by a static friction force acting between a surface 88d in the opening region 112d of the recess 38d and the frictional element 42d.
In Figure 7, a fifth variant of a return-momentum reducing unit 16e of a protective device 1Oe is represented, provided for the purpose of at least partially preventing rebound of a second protective hood 14e when a protecting position is reached when moving from a working position into the protecting position. A capturing unit 22e has a capturing element 24e, which is formed by a recess 38e, and a capturing element 26e, which is formed by a latching element 46e. The recess 38e is formed in a rectangular shape and provided for the purpose of receiving a further capturing element 3Oe of the capturing unit 22e, which is arranged on a housing and/or a guiding unit. The lashing element 46e is arranged in an opening region 112e of the recess 38e on a side wall 122e of the recess 38e, so that an opening 78e of the recess 38e is made smaller and a cross-sectional area 116e of the opening region 112e is thereby smaller than a maximum cross-sectional area 12Oe of the further capturing element 3Oe. The further capturing element 3Oe is formed by a latching element 48e and mounted movably on the housing and/or the guiding element, the lashing element 48e being formed by a catch and thereby arranged such that it can rotate about an axis 124e in a direction of rotation 126e. A partial region 128e of the latching element 48e that is arranged inwards in a radial direction 8Oe of the latching element 48e is provided for the purpose of rotatable mounting on the housing and/or the guiding unit. A partial region 130e of the latching element 48e that is on the outside in the radial direction 8Oe is formed as a star-shaped serration 132e, so that, when a second protective hood 14e moves into the protecting position, the latching element 46e of the second protective hood 14e can engage between two teeth of the serration 132e and the latching element 48e can rotate into the recess 38e. On account of the latching element 48e, formed as a catch, together with the latching element 46e, the second protective hood 14e is secured in the protecting position when this position is reached, and rebounding of the second protective hood 14e is thereby prevented. For the second protective hood 14e to move out of the protecting position, the return-momentum reducing unit 16e may have an additional triggering element (not represented any more specifically here) , which triggers a securing action of the catch.
In Figure 8, an alternative configuration of the return-momentum reducing unit 16f of the protective device 1Of in comparison with Figure 7 is represented, provided for the purpose of at least partially preventing rebound of a second protective hood 14f when a protecting position is reached when moving from a working position into the protecting position. A capturing element 3Of of a capturing unit 32f that is arranged on a housing and/or a guiding unit differs from the capturing element 3Oe in Figure 7 to the extent that teeth of a serration 132f of the capturing element 3Of are arranged arcuately in a crescent shape in a direction of rotation 126f, in which the capturing element 3Of rotates when a capturing element 24f of the second protective hood 14f that is formed by a recess 38f is introduced.
In Figure 9, a seventh variant of a return-momentum reducing unit 16g of a protective device 1Og is represented, provided for the purpose of at least partially preventing rebound of a second protective hood 14g when a protecting position is reached when moving from a working position into the protecting position. A capturing unit 22g of the return-momentum reducing unit 16g has a capturing element 24g, which is formed by a rectangular recess 38g, and two capturing elements 26g, 28g, which are respectively formed by a latching element 46g, 50g. The latching elements 46g, 50g are arranged on opposite side walls 122g, 134g of the recess 38g by analogy with the latching element 46f of the recess 38f from Figure 7. The capturing unit 22g has a further capturing element 30g, which is formed as a latching element 48g and is arranged on a housing and/or a guiding unit. The further capturing element 3Og is conically formed along its principal direction of extent 136g, the further capturing element 3Og being formed such that it tapers counter to a direction of movement 18g of the second protective hood 14g into the protecting position. A cross-sectional area 116g of an opening region 112g of the recess 38g is in this case formed such that it is smaller than a maximum cross-sectional area 12Og of the further capturing element 3Og and larger than a cross-sectional area 14Og of a tapered partial region 138g of the capturing element 3Og. A partial region 142g with the maximum cross-sectional area 120g is also adjoined by a partial region 144g of the capturing element 30g with a cross-sectional area that is smaller than the cross- sectional area 116g of the recess 38g and, in a protecting position of the second protective hood 14g, protrudes from the recess 38g along the direction of movement 18g of the second protective hood 14g, so that canting of the further capturing element 30g in the recess 38g is prevented. When the second protective hood 14g moves into the protecting position, the further capturing element 30g is thereby introduced into the recess 38g until the partial region 142g with the maximum cross-sectional area 120g has been guided past the two latching elements 46g, 50g, and rebounding of the second protective hood 14g is prevented on account of the larger cross-sectional area 120g. Moreover, on account of the tapered form of the further capturing element 30g, kinetic energy of the second protective hood 14g is converted into frictional energy or thermal energy when the second protective hood 14g moves into the protecting position, in that a static friction force acts between two latching elements 46g, 50g and a surface 86g of the further capturing element 30g. Furthermore, the further capturing element 30g may be formed from elastic material, such as for example rubber, so that a slowing down effect of the second protective hood 14g can be intensified. In Figure 10, an eighth variant of a return-momentum reducing unit 16h of a protective device 1Oh is represented, provided for the purpose of at least partially preventing rebound of a second protective hood 14h when a protecting position is reached when moving from a working position into the protecting position. This exemplary embodiment differs from the exemplary embodiment in Figure 9 by an alternative configuration of a further capturing element 3Oh of a capturing unit 22h. The further capturing element 3Og is formed by a latching element 48h, which is formed in a substantially cuboidal shape with a comb-like profiling 146h. When the second protective hood 14h moves into the protecting position, teeth 148h of the comb-like profiling 146h are pressed against latching elements 48h, 5Oh of a capturing element 24h of the second protective hood 14h counter to a resilient force of the teeth 148h, until the latter elastically deform in such a way as to make it possible for the further capturing element 30h to move into a recess 38h. The teeth 148h of the comb-like profiling 146h thereby act in a movement-damping manner, in that they resiliently counteract the movement of the second protective hood 14h or a resilient force of the teeth 148h counteracts the movement of the second protective hood 14h.
In Figure 11, a ninth variant of a return-momentum reducing unit 16i of a protective device 1Oi is represented, provided for the purpose of at least partially preventing rebound of a second protective hood 14i when a protecting position is reached when moving from a working position into the protecting position. A capturing unit 22i has a capturing element 24i, which is formed by a recess 38i, and a capturing element 26i, which is formed by a magnet 52i. The magnet 52i is in this case formed by a surface layer 150i that is formed by a permanent magnet. The recess 38i is of a rectangular shape. The capturing unit 22i also has a further capturing element 3Oi, which is likewise formed in a cuboidal shape and thereby has a smaller cross-sectional area 12Oi than a cross- sectional area 116i of the recess 38i. The further capturing element 3Oi is likewise formed by a magnet 54i, which is formed by a surface layer 152i that is formed by a permanent magnet. The two magnets 52i, 54i are respectively formed by a magnetic North pole 19Oi, 194i and a magnetic South pole 192i, 196i, the magnetic North pole 19Oi of the magnet 52i of the protective hood 14i lying against a magnetic South pole 196i of the magnet 54i and the magnetic South pole 192i lying against a magnetic North pole 194i of the magnet 52i in a protecting position, so that a magnetic force of attraction acts between the second protective hood 14i and the further capturing element 3Oi in a protecting position of the second protective hood 14i, preventing the second protective hood 14i from rebounding from the protecting position. A magnetic force which acts between the two magnets 52i, 54i in the protecting position is advantageously greater than a rebound force of the second protective hood 14i.
In Figure 12, an alternative configuration of a return- momentum reducing unit 16 j of a protective device 10j in comparison with Figure 11 is represented, provided for the purpose of at least partially preventing rebound of a second protective hood 14j when a protecting position is reached when moving from a working position into the protecting position. The exemplary embodiment in Figure 12 differs from the exemplary embodiment from Figure 11 by an alternative configuration of capturing elements 24j, 36j, 30j of the capturing unit 22 j. The capturing elements 24 j, 26j arranged on the second protective hood 14j are formed by a U-shaped recess 38 j and a magnet 52j, which is formed as a surface layer 150j that is formed by a permanent magnet. The further capturing element 30j is formed in a cylindrical shape by analogy with the exemplary embodiment in Figure 2 and has a magnet 54 with a surface layer 152j that is formed by a permanent magnet .
In Figures 13 to 15, an eleventh variant of a return- momentum reducing unit 16k of a protective device 10k is represented, provided for the purpose of preventing rebound of a second protective hood 14k when a protecting position is reached when moving from a working position into the protecting position. The return-momentum reducing unit 16k has a capturing unit 22k and a slowing down unit 154k. The capturing unit 22k comprises a capturing element 24k, which is formed by a U-shaped recess 38k and is arranged on the second protective hood 14k. A further capturing element 30k of the capturing unit 22k is arranged on a housing 34k and/or a guiding unit and is formed in a cylindrical shape. The further capturing element 30k also has a capturing region 156k, which is formed by a groove- shaped recess 40k extending in a circumferential direction 96k around the capturing element 30k. In a protecting position of the second protective hood 14k, side walls 122k, 134k of the recess 38k of the second protective hood 14k lie against side walls 160k of the capturing region 156k of the further capturing element 30k, a static friction force that holds the second protective hood 14k in the protecting position (Figures 13 and 14) acting between the side walls 122k, 134k, 160k. To open the second protective hood 14k from the protecting position, such as for example to commence sawing operation, here it is merely necessary for an operator to overcome a small frictional resistance between the protective hood 14k and the capturing element 30k.
The slowing down unit 154k is formed by an air damping unit 21k. The air damping unit 21k has a slowing down element 162k, which is formed by a cavity in a wall 164k of the protective hood. The cavity has two channels 166k, 168k, which are arranged in an L-shaped manner in relation to each other, and two openings 170k, 172k, which are respectively arranged at an end region 174k, 176k of a channel 166k, 168k (Figure 15) . The first channel 166k extends from an end region 178k of the recess 38k into the second protective hood 14k, a principal direction of extent 180k of the recess 38k being aligned parallel to a principal direction of extent 182k of the first channel 166k. The second channel 168k is arranged substantially perpendicular to the first channel 166k. A cross-sectional area 184k of the first channel 166k (shown hatched in Figure 15) is in this case larger than a cross-sectional area 186k of the second channel 168k (shown hatched in Figure 15) . The opening 170k of the first channel 166k is arranged in a region of the recess 38k and has a larger cross- sectional area 184k than a cross-sectional area 186k of the opening 172k of the second channel 168k (Figures 14 and 15) .
When the second protective hood 14k moves into the protecting position, a closed space 188k is formed shortly before reaching the protecting position by means of the recess 38k of the second protective hood 14k and by means of the side walls 160k of the further capturing element 30k that delimit the capturing region 156k (Figure 14) . In this space 188k, the air contained in it is enclosed and can only escape through the slowing down element 162k or the two channels 166k, 168k. On account of the large cross-sectional area 184k, a large amount of air per unit of time can force its way into the channels 166k, 168k through the opening 170k of the first channel 166k. Escape of the air can only take place through the opening 172k of the second channel 168k, the small cross-sectional area 186k of the opening 172k having the effect that a smaller amount of air per unit of time can escape here than the amount of air that can at the same time force its way in through the opening 170k with the large cross-sectional area 184k. As a result, a positive pressure is built up in the first channel 166k and in the closed space 188k. This positive pressure has the effect of producing a force which is directed counter to a movement, in particular a speed, of the second protective hood 14k into the protecting position. The force becomes greater the more the protective hood 14k continues its movement into the protecting position, and consequently the positive pressure of air in the enclosed space 188k increases further. It is possible in this way for a speed of the second protective hood 14k to be slowed down or kinetic energy of the second protective hood 14k to be converted into internal energy of the enclosed air. When the protecting position is reached, the speed of the second protective hood 14k is consequently slowed down and/or reduced almost completely, so that the second protective hood 14k comes substantially to a standstill in the protecting position and rebounding of the second protective hood 14k is at least reduced. Moreover, possible return momentum, which can be transferred from the housing 34k and/or the guiding unit to the second protective hood 14k on account of a low residual speed of the second protective hood 14k when the protecting position is reached, is absorbed by the static friction force acting between the protective hood 14k and the capturing element 30k arranged on the housing 34k and/or the guiding unit, so that the second protective hood 14k is secured in the protecting position, and consequently greatest possible protection for an operator can be achieved.