1. A furniture drive system (4) for a furniture part (3) movably-supported on a
furniture carcass (2), including:
- a mechanical actuating unit (5) with:
- at least one pivotally mounted actuating arm (6) for moving the movable furniture part (3),
- a spring device (18) for applying a force to the actuating arm (6),
- a movably-mounted actuating portion (10) having a transmission opening (10a) for transmitting a force from the spring device (18) to the actuating arm (6),
- an electrical drive unit (7) with:
- an electric motor (12) for the electromotive support of a movement of the movable furniture part (3),
- an entrainment member (22) configured to be driven by the electric motor (12) for transmitting a torque from the electric motor (12) to the mechanical actuating unit (5), wherein the entrainment member (22) of the electrical drive unit (7) can be engaged into the transmission opening (10a) of the actuating portion (10),
wherein the electrical drive unit (7) and the mechanical actuating unit (5) are configured as separate constructional units which can be fixed to one another, characterized in that an abutment surface (25) for the entrainment member (22) is arranged laterally besides the transmission opening (10a), and that the entrainment member (22) is pre-stressed by an energy storage member (23) in a direction towards the abutment surface (25), wherein the entrainment member (22) in a position, in which the entrainment member (22) is aligned flush with the transmission opening (10a), automatically penetrates into the transmission opening (10a) by the force of the energy storage member (23).
2. The furniture drive system according to claim 1, characterized in that the position
in which the entrainment member (22) is aligned flush with the transmission

opening (10a), can be adjusted by a movement of the actuating arm (6) and/or by a movement of the electric motor (12).
3. The furniture drive system according to claim 1 or 2, characterized in that the abutment surface (25) is formed by the actuating portion (10).
4. The furniture drive system according to one of the claims 1 to 3, characterized in that the actuating portion (10) has at least one ramp (24, 24a) by which the entrainment member (22) can be lifted, starting from a lower position with respect to the abutment surface (25), in a direction towards the abutment surface (25) against the force of the energy storage member (23).
5. The furniture drive system according to one of the claims 1 to 4, characterized in that the entrainment member (22) is arranged on a movably-mounted transmission element (14) of the electrical drive unit (7), wherein the transmission element (14) is configured to be driven by the electric motor (12).
6. The furniture drive system according to claim 5, characterized in that the movably-mounted transmission element (14) is pivotally mounted about a pivoting axis (15).
7. The furniture drive system according to claim 5 or 6, characterized in that the movably-mounted transmission element (14), at least over a region, has a tooth arrangement (16), preferably an eccentric tooth arrangement.
8. The furniture drive system according to one of the claims 5 to 7, characterized in that the entrainment member (22) is linearly displaceably guided relative to the transmission element (14) by at least one guide (26).
9. The furniture drive system according to one of the claims 1 to 8, characterized in that the energy storage member (23) includes at least one compression spring.
10. The furniture drive system according to one of the claims 5 to 9, characterized in that the transmission element (14) has a supporting element (17), wherein the

energy storage member (23) cooperates with the supporting element (17) one the one hand and with the entrainment member (22) on the other hand.
11. The furniture drive system according to one of the claims 1 to 10, characterized in that the mechanical actuating unit (5) has at least one bearing location (28a, 28b) into which the electrical drive unit (7) can be engaged, and that the electrical drive unit (7) being engaged into the at least one bearing location (28a, 28b) can be pivoted about an axis, which preferably extends horizontally in the mounting condition, in a direction towards the mechanical actuating unit (5) and that a locking device (30) is provided by which the mechanical actuating unit (5) can be releasably locked with the electrical drive unit (7).
12. The furniture drive system according to claim 11, characterized in that the locking device (30) includes at least one movably-mounted locking lever (30a) and at least one locking element (31a) configured to be moved by the locking lever (30a), wherein the locking element (31a) can be locked relative to a recess (32a) arranged on the mechanical actuating unit (5) or on the electrical drive unit (7) upon an actuation of the locking lever (30a).
13. The furniture drive system according to claim 12, characterized in that the locking device (30) includes at least two or a plurality of locking elements (31a, 31b) which are motionally coupled to the locking lever (30a), so that the locking elements (31a, 31b) can jointly be moved upon an actuation of the locking lever (30a) and can be synchronously locked and/or synchronously unlocked relative to corresponding recesses (32a, 32b).
14. An item of furniture (1) with a furniture carcass (2) and with a furniture part (3) movably supported on the furniture carcass (2), and with a furniture drive system according to one of the claims 1 to 13 for driving the movable furniture part (3).
15. A method for mounting an electrical drive unit (7) to a mechanical actuating unit (5) for moving a movably-supported furniture part (3), wherein the mechanical

actuating unit (5) includes at least one pivotally mounted actuating arm (6), wherein a movement of the actuating arm (6) is being supported by an entrainment member (22) configured to be driven by an electromotor (12) of the electrical drive unit (7) in an electromotive manner, wherein the entrainment member (22) of the electrical drive unit (7) can be engaged into an transmission opening (10a) of the mechanical actuating unit (5), characterized by the following steps:
- mounting the mechanical actuating unit (5) to a furniture carcass (2),
- fixing the electrical drive unit (7) to the mechanical actuating unit (5),
- moving the pivotally mounted actuating arm (6) of the mechanical actuating unit (5) and/or moving the electric motor (12) of the electric drive device (7), wherein the entrainment member (22) is pre-stressed in a direction of an abutment surface (25) of the mechanical actuating unit (5) and can be guided along the abutment surface (25) by a movement of the actuating arm (6) and/or by a movement of the electric motor (12),
- wherein the actuating arm (6) and/or the electric motor (12) are moved as long as the entrainment member (22) of the electrical drive unit (7) automatically penetrates into transmission opening (10a) of the mechanical actuating unit (5) by the force of the energy storage member (23).