The invention relates to a motor with permanent magnets, comprising a first part and a second part, one of the parts being movable with respect to the other part in a predetermined direction of movement, and the parts being separated from one another by a gap. Motors based on the use of magnetic fields are generally known. Such magnetic fields can be generated by permanent magnets, or by- electric conductors which are energized by a direct current or a current varying over time. A drawback of the use of electric conductors for generating a magnetic field is that electric energy has to be supplied to the electric conductors, which are usually formed in the shape of a coil. In this case, complicated electric structures are required in order to produce and control the currents and voltages used, while additionally, slip ring and/or commutator structures are required in order to transfer the electric energy to moving, in particular rotating, conductors. No supply of electric or other energy is required in order to use permanent magnets for generating a magnetic field, except for the energy which is required in order to permanently magnetize a suitable material once. It is an object of the invention to provide a motor based on the use of magnetic fields, in which the magnetic fields are exclusively generated by the use of permanent magnets. This object is achieved in that the first part of the motor according to the invention comprises: a first series of spaced-apart permanent magnets arranged in said direction of movement, each having two opposite poles, a first one of the poles of each permanent magnet being arranged near the gap and a second one of the poles of each permanent magnet being arranged at a distance from the gap; a second series of spaced-apart permanent magnets arranged in said direction of movement between the permanent magnets of the first series, each having two opposite poles, a second one of the poles of each permanent magnet of the second series being arranged near the gap at the first one of the poles of a permanent magnet of the first series in order jointly to form a double pole, and a first one of the poles of each permanent magnet of the second series being arranged at a distance from the gap near the second one of the poles of a permanent magnet of the first series, the adjoining permanent magnets of the first and second series being oriented at an angle with respect to one another, and the second part comprises: a third series of spaced-apart permanent magnets arranged in said direction of movement, each having two opposite poles, a first one of the poles of each permanent magnet being arranged near the gap in order to form a single pole, and a second one of the poles of each permanent magnet being arranged at a distance from the rotor surface; and the number of double poles not being equal to the number of single poles. As is known, opposite poles of permanent magnets attract one another and like poles of permanent magnets repel one another. With the motor according to the invention, optimum use is made of this phenomenon in order to generate mechanical power by the first part and the second part moving with respect to one another. The first part may be, for example, a stator of the motor, and the second part a rotor, but the first part may also be a rotor of the motor and the second part the stator. In this case, the expressions "stator" and "rotor" should be interpreted broadly: the stator and rotor may form part of a rotating motor, which may involve a rotor situated inside the stator or a rotor situated outside the stator, and may involve a random spatial orientation of the axis of rotation of the motor, such as horizontal or vertical. The stator and the rotor may also form part of a randomly oriented linear motor, the stator comprising a multiple of the stator lengths associated with the rotor length. In the motor according to the present invention, the permanent magnets of the first part are oriented at an angle to the gap, a double pole being encountered in each case when moving in said direction of movement along the gap, consisting of a first pole of a permanent magnet of the first series adjoining a second pole of a permanent magnet of the second series. Furthermore, when moving in said direction of movement along the gap, in each case a single pole is encountered consisting of a first pole of a permanent magnet of the third series. The permanent magnets of the third series are oriented at an angle with respect to the gap, for example in the range 30°-90°. The orientation of the permanent magnets of the first series relative to the second series is chosen such that they affect one another as little as possible. In an embodiment of the motor according to the invention, the second part furthermore comprises a fourth series of spaced-apart permanent magnets arranged in said direction of movement between the permanent magnets of the third series, each having two opposite poles, a first one of the poles of each permanent magnet of the fourth series being arranged near the gap at the first one of the poles of a permanent magnet of the third series in order to jointly form a single pole, and a second one of the poles of each permanent magnet of the fourth series being arranged at a distance from the gap near the second one of the poles of a permanent magnet of the third series, the adjoining permanent magnets of the third and fourth series being oriented at an angle with respect to one another. It should be noted that the first poles of the permanent magnets of the first and second series are the same as, or opposite to the first poles of the permanent magnets of the third and fourth series. In a configuration of this kind, viewed in said direction of movement, the single poles, prior to reaching a double pole, will be attracted by the double pole and, after having passed the double pole, will be repelled by the double pole, following which the respective single pole is attracted by the next double pole, etc. This results in a movement of the first and second part relative to one another, with the motor being able to supply power. For an optimum operation of the motor as regards attracting and repelling effect between the single poles of the second part and the double poles of the first part, in an embodiment the orientation of the permanent magnets of the first series relative to the gap differs from the orientation of the permanent magnets of the second series relative to the gap, and/or the orientation of the permanent magnets of the third series relative to the gap differs from the orientation of the permanent magnets of the fourth series relative to the gap in order to generate as much power as possible in the direction of movement of the motor. In the opposite direction, it will thus be possible to generate a braking force which is as large as possible. In order to optimize the operation of the motor further, in one embodiment, the distance between the poles of each of the permanent magnets of the first series is not equal to the distance between the poles of each of the permanent magnets of the second series, and/or the distance between the poles of each of the permanent magnets of the third series is not equal to the distance between the poles of each of the permanent magnets of the fourth series. The number of double poles is not equal to the number of single poles, with the double poles and the single poles assumed to be spaced apart equidistantly. More particularly, the number of double poles and the number of single poles are prime numbers, i.e. numbers which have been chosen from the series 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, etc. By selecting the number of double poles to be different from the number of single poles, a preferred position of the first part with respect to the second part, and thus a slowing down of the parts relative to one another can be avoided. In a further embodiment, the first part comprises a fifth series of permanent magnets, each having two opposite poles, a first one of the poles of each permanent magnet of the fifth series being arranged at a distance from the gap at the second one of the poles of a permanent magnet of the first series, and a second one of the poles of each permanent magnet of the fifth series being arranged at a distance from the gap at the first one of the poles of a permanent magnet of the second series. In this manner, the magnetic field of the sets of permanent magnets which form a double pole is influenced in order to optimize the operation of the motor further. In an embodiment, the rotor comprises a sixth series of permanent magnets, each having two opposite poles, a first one of the poles of each permanent magnet of the sixth series being arranged near the gap at the first one of the poles of a permanent magnet of the third and fourth series, and a second one of the poles of each permanent magnet of the sixth series being arranged at a distance from the gap. The presence of the permanent magnets of the sixth series amplifies the magnetic field at the single poles, as a result of which the operation of the motor is optimized further. Preferably, the permanent magnets of the sixth series are arranged between the pairs of permanent magnets of the third and fourth series which adjoin one another at the gap. In an embodiment, the permanent magnets are substantially panel-shaped. In particular, they are substantially rectangular, the first and second pole of the permanent magnets being located at opposite sides of the permanent magnets. The starting material for such magnets can be formed and magnetized in a simple manner, and the permanent magnets obtained in this manner can easily and relatively inexpensively be incorporated in a construction comprising the first and second parts. A material which may advantageously be used for the production of the permanent magnets is silver steel. Once the motor according to the present invention has finally been assembled, the first part and the second part will tend to move relative to one another. If it is undesirable to start this movement, or if a moving part needs to be slowed down or stopped, a facility on the motor is required. In an embodiment, at least one of the first and second parts comprises at least two sub-parts which can be displaced in a direction different from said direction of movement relative to the other one of the first and second parts. Such a displacement of the stator parts reduces the magnetic interaction between the stator and the rotor, following which the motor will come to a standstill as a result of the inherent friction produced therein, optionally also by the use of a braking construction, such as a mechanical disc brake. In an embodiment, each sub-part can be displaced in a direction substantially perpendicular to the gap and/or each sub-part can be displaced in a direction substantially parallel to the gap. In the latter case, each sub-part is preferably displaceable in a direction substantially perpendicular to said direction of movement. Other claims, features and advantages of the invention will become clear with reference to the accompanying drawings, which illustrate a non-limiting exemplary embodiment, in which: Fig. 1 shows a front view of a motor according to the invention; Fig. 2 shows a side view of the motor according to Fig. 1; Fig. 3 shows a section through a stator and a rotor of the motor according to Fig. 2 along the line III-III; Fig. 4 illustrates the position of permanent magnets in the stator and the rotor according to Fig. 3; Fig. 5A shows a front view of the stator according to Fig. 3; Fig. 5B shows a side view of the stator according to Fig. 5A; Fig. 5C shows a part of the stator according to Fig. 5A; Fig. 6A shows a front view of the rotor according to Fig. 3; Fig. 6B shows a side view of the rotor according to Fig. 6A; Fig. 6C shows a part of the rotor according to Fig. 6A; Fig. 7 diagrammatically illustrates a facility for bringing a motor according to the invention to a standstill; Figs. 8A, 8B and 8C diagrammatically show various stages when a facility for bringing a motor according to the invention to a standstill is being used; and Fig. 9 illustrates another facility for bringing a motor according to the invention to a standstill. The same reference numerals in the various Figures relate to the same parts or parts having a similar function. Figs. 1 and 2 show an embodiment of the motor according to the invention as a rotating machine. Inside a substantially cylindrical housing 2, there are a rotor and a stator, which are shown in more detail in the following Figures. The stator is fixedly connected to the housing 2, which in turn is fixedly connected to the bearing structures 4 and 6 for mounting a shaft 8 connected to the rotor. The bearing structures 4, 6 are supported via legs 10 on a base 14 connected to a floor 12. Fig. 3 shows a stator 16 which is substantially in the shape of a cylinder shell and a substantially cylindrical rotor 18, which are separated from one another by an air gap 20. The gap 20 can also be filled with a gas other than air, or with a liquid, or be turned into a vacuum. As Figs. 3 and 5A-5C show, the stator 16 comprises a number of support blocks 22, in the embodiment shown nineteen, which are made, for example, of plastic or metal or a combination thereof. The support blocks 22 extend over some distance in a direction perpendicular to the plane of the drawing. The support blocks 22 taper in the radial direction from the stator surface 24 facing the air gap 20 to the side 26 facing away from the air gap 20, with an angle α between a radial line 28 and a first side 30 of each support block 22 being different to an angle β between a radial line 28 and a second side 32 of the support block 22 located opposite the first side 30. In the embodiment shown, the angle α is smaller than the angle β, but this may also be reversed. The angles a and β may also be equal. They are between 0° and 90°, more particularly between 30° and 60°. The support blocks 22 are arranged and enclosed between flanges 34, which are, for example, made from a non-magnetizable material, such as aluminium or plastic or a combination thereof. Panel-shaped permanent magnets 36 and 38, respectively, are positioned along the sides 30, 32 of each of the support blocks 22. The stator 16 also comprises optional panel-shaped permanent magnets 40 which extend between the edges of the adjoining magnets 36, 38 facing away from the air gap 20. The configuration of the magnetic fields generated by the magnets 36, 38 and 40 is discussed in more detail below with reference to Fig. 4. As Figs. 3 and 6A-6C show, the rotor 18 comprises a number of, in the embodiment shown seventeen, support blocks 42, which are made from, for example, plastic or metal or a combination thereof. The support blocks 42 extend over some distance in a direction perpendicular to the plane of the drawing. The support blocks 42 taper in the radial direction from the rotor surface 44 facing the air gap 20 to the central section of the rotor 18, with an angle γ between a radial line 28 and a first side 46 of each support block 42 being different from an angle δ between a radial line 28 and a second side 48 of the support block 42 located opposite the first side 46. In the embodiment shown, the angle γ is smaller than the angle δ, but this may also be reversed. The angles γ and δ may also be equal. They are between 0° and 90°, more particularly between 30° and 60°. Preferably, the angle a is substantially equal to the angle γ, and the angle β is substantially equal to the angle δ, but this is not essential. In the embodiment shown, the fact that the angles α and γ are smaller than the angles β and δ causes the rotor 18 to move in the direction indicated by arrow 49. The support blocks 42 are arranged and enclosed between flanges 50, which are, for example, made from a non-magnetizable material, such as aluminium or plastic or a combination thereof. Panel-shaped permanent magnets 52 and 54, respectively, are positioned along the sides 46, 48 of each of the support blocks 42. The rotor 16 also comprises optional panel-shaped permanent magnets 56 which are oriented in radial direction and an edge of which facing the air gap 20 is positioned near the edges of the magnets 52, 54 facing the air gap 20. The configuration of the magnetic fields generated by the magnets 52, 54 and 56 is discussed in more detail below with reference to Fig. 4. The rotor comprises a central opening 58 provided with a key way for receiving the shaft 8. Fig. 4 shows the cross-sections, the positions and orientations of the permanent magnets 36, 38, 40, 52, 54 and 56, the magnets extending over some distance in a direction perpendicular to the plane of the drawing. Near the respective edge of the magnets, the position of a pole of each of the permanent magnets has also been indicated, with a λλ+"-sign indicating a north pole or a south pole, and a "-"-sign the opposite pole. The permanent magnets 36 and 38 of the stator 16 thus have opposite poles on their edges facing the stator surface 24, while the permanent magnets 52, 54 and 56 of the rotor 18 have similar poles on their edges facing the rotor surface 44. The poles of the magnets 40 are situated at opposite poles of the adjoining magnets 36 and 38. It will be clear that the direction of rotation 49 of the motor remains the same when the polarity of the permanent magnets of the rotor and those of the stator is inverted. The direction of rotation of the motor will reverse when either the polarity of the permanent magnets of the stator or the polarity of the permanent magnets of the rotor is inverted while the polarity of the rotor or stator remains the same, respectively. In the situation according to Fig. 4, when the rotor 18 is moved counter to direction 49, a braking force will have to be overcome. Fig. 7 shows a housing 21 with a stator 16 accommodated therein (not shown) . The housing comprises two housing parts 21a and 21b with associated respective stator parts which can pivot about an axis 23 with respect to one another between a position in which the housing parts 21a, 21b are lying against one another (not shown) and a position in which the housing parts 21a, 21b are at a distance from one another (shown), it being possible for the part 21a to be tilted upwards by means of an actuator 25a which is fixedly arranged relative to the base 14 and is coupled to an arm 27a fastened to the part 21a so as to be able to pivot, and it being possible for the part 21b to be tilted downwards by means of an actuator 25b which is fixedly arranged relative to the base 14 and is coupled to an arm 27b fastened to the part 21b so as to be able to pivot. Thus, the stator parts attached to the housing 21 can be brought together, which is the normal operating position, and can be moved at a distance from one another in order to reduce the magnetic interaction between the stator parts and the rotor and thereby stop the motor. It is obviously also possible to arrange a similar structure 25a, 25b, 27a, 27b on the side of the axis 23 of the housing 21 as on the opposite side, the connection between the parts 21a and 21b via the axis 23 being redundant. In this manner, the parts 21a and 21b can move towards one another and away from one another along a line 29. Figs. 8A, 8B and 8C successively respectively show a rotor 18 which is situated inside a stator 16 during a normal operating state, a rotor 18 which has been partially displaced in an axial direction relative to the stator 16 (it being possible for the rotor 18 to be displaced axially when the stator 16 has a fixed position or the stator 16 to be displaced axially when the rotor 18 has a fixed position, or the stator 16 and the rotor 18 both being displaced), and a further displacement of the rotor 18 with respect to the stator 16. As a result of the displacement, the magnetic interaction between the stator 16 and the rotor 18 decreases, as a result of which the motor can be taken out of service. Fig. 9 illustrates how the shaft 8 of the motor can be provided with a disc 60 on which a braking unit 62 can engage in order to slow down and stop the rotor 18 of the motor.