EP0065980A1

EP0065980A1 - Orbital movement apparatus

Info

Publication number: EP0065980A1
Application number: EP19820900206
Authority: EP
Inventors: Robert C. Geschwender
Original assignee: Concept Engineering Inc
Current assignee: Concept Engineering Inc
Priority date: 1980-12-03
Filing date: 1981-12-02
Publication date: 1982-12-08
Also published as: WO1982001923A1

Abstract

Dispositif a mouvement orbital comprenant un premier (3) et un deuxieme (5) organes, un arbre (7) tourillonne dans le premier organe (3), et un excentrique (11) sur l'arbre possedant un axe (AX2) generalement parallele a l'axe (AX1) de l'arbre mais eloigne radialement d'une distance predeterminee de celui-ci, l'excentrique (1) etant tourillonne dans le deuxieme organe (5). Les organes possedent des surfaces planes generalement opposees (15, 17) disposees generalement parallelement et en face a face l'une par rapport a l'autre. Au moins trois connexions (19) entre les organes (3, 5) permettent un mouvement orbital tout en empechant un mouvement rotatif du deuxieme organe (5) par rapport au premier organe (3) lors de la rotation relative entre l'arbre (7) et le premier organe (3). Chaque connexion (19) comprend une paire de renfoncements opposes (21) sur les surfaces planes opposees (15, 17) des organes, les renfoncements (21) etant concaves, generalement de forme circulaire et de tailles sensiblement identiques, l'axe central (AX3) d'un renfoncement (21) dans chaque paire etant sensiblement parallele a l'axe central (AX4) de l'autre renfoncement (21) de la paire mais decale de cet axe d'une distance predeterminee, et une bille (23) est logee dans chaque paire de renfoncements (21). Les renfoncements opposes (21) de chaque paire possedent des parois peripheriques arrondies vers l'interieur formant des chemins circulaires pour les billes respectives (23), ce qui provoque, lors de la rotation relative entre le premier organe (3) et l'arbre (7), le roulement de la bille (23) le long des chemins circulaires, ce qui donne lieu a un mouvement orbital tout en empechant un mouvement rotatif du deuxieme organe (5) par rapport au premier organe (3).Orbital motion device comprising first (3) and second (5) organs, a shaft (7) journalled in the first organ (3), and an eccentric (11) on the shaft having a generally parallel axis (AX2) to the axis (AX1) of the shaft but radially away from a predetermined distance therefrom, the eccentric (1) being journalled in the second member (5). The members have generally opposed planar surfaces (15, 17) generally arranged parallel and face to face with respect to each other. At least three connections (19) between the members (3, 5) allow an orbital movement while preventing a rotary movement of the second member (5) relative to the first member (3) during the relative rotation between the shaft (7 ) and the first organ (3). Each connection (19) comprises a pair of opposite recesses (21) on the opposite flat surfaces (15, 17) of the members, the recesses (21) being concave, generally of circular shape and of substantially identical sizes, the central axis ( AX3) of a recess (21) in each pair being substantially parallel to the central axis (AX4) of the other recess (21) of the pair but offset from this axis by a predetermined distance, and a ball (23 ) is housed in each pair of recesses (21). The opposite recesses (21) of each pair have peripheral walls rounded inwards forming circular paths for the respective balls (23), which causes, during the relative rotation between the first member (3) and the shaft (7), the rolling of the ball (23) along the circular paths, which gives rise to an orbital movement while preventing a rotary movement of the second member (5) relative to the first member (3).

Description

ORBITAL MOVEMENT APPARATUS Background of the Invention

This invention relates generally to mechanical movement mechanisms capable of converting rotary movement to orbital movement and vice versa.

Orbital movement mechanisms are widely used in mechanical power transmission devices. One of the most common of such mechanisms may be found in conventional speed reducers, for example, wherein the input shaft of the unit is journalled in one mechanical part (e.g., the frame) and is formed with an eccentric thereon which is journalled in a second mechanical part (e.g., a gear wheel). Upon rotation of the input shaft, movement of the second part is limited to simple orbital movement (without rotation) with respect to the first part by cylindrical rollers rotatably mounted on pins projecting in cantilever fashion from the first part into holes in the second part. As the second part orbits, the pin-mounted rollers roll around the peripheral surfaces of the holes. This type of mechanism has several drawbacks, one of the most serious being the relatively large amount of friction generated during orbital movement. This friction derives from two sources, namely, from the rolling contact between the rollers and the peripheral surfaces of the holes, and from the rotation of the rollers on their respective pins. Moreover, in this latter regard, the cantilever pins tend to deflect when subjected to a load, causing the rollers thereon to bind against the edges of the holes. These friction losses result in a considerable reduction in efficiency. Another disadvantage of this type of system is that separate means of some type (e.g., a sleeve) is required to maintain the opposing faces of the two mechanical parts spaced apart and generally parallel. Reference may be made to U.S. pa ten t s 1,089,181, 3,975,973, 3,145,585, 3,710,635, 1,844,471 and 1,862,220 for devices generally relevant to this invention. Summary of the Invention Among the several objects of this invention may be noted the provision of an improved orbital movement mechanism or apparatus for converting rotary movement to orbital movement and vice versa; the provision of such a mechanism which reduces frictional losses for greater efficiency; the provision of such a mechanism which effects orbital movement of one mechanical part with respect to another while maintaining opposing faces of the parts generally parallel; the provision of such a mechanism or apparatus which is simple in design; and the provision of such a mechanism or apparatus which is durable.

An orbital movement mechanism or apparatus of the present invention comprises first and second members, a shaft journalled in the first member, and an eccen tr ic on the shaft having an axis generally parallel to but radially offset a predetermined distance from the axis of the shaft, the eccentric being journalled in the second member. The members have opposing generally planar surfaces disposed generally parallel to and face-to-face with one another. The apparatus also includes means for coupling the members to permit orbital movement, while preventing rotational movement, of the second member with respect to the first member upon relative rotation between the shaft and the first member. This means comprises at least three connections between the members, each connection comprising a pair of opposing recesses in the planar surfaces of the members, the recesses being gene r ally circular in shape and substantially identical in size with the central axis of one recess of each pair being substantially parallel to and offset from the central axis of the other recess of the pair by said predetermined distance, and a ball in each said pair of recesses, the combined depths of the opposing recesses being less than the diameter of the ball for maintaining the aforesaid planar surfaces spaced apart. The opposing recesses of each pair have peripheral walls providing circular races for the respective ball whereby on relative rotation between the first member and the shaft the ball rolls around the races with the center of the ball tracing a circle having a diameter approximately equal to the aforesaid predetermined distance thereby to permit orbital movement, while preventing rotational movement, of the second member with respect to the first member, the orbital movement being such that a point on the second member traces a circle with respect to the first member, the diameter of the latter circle being approximately equal to twice said predetermined distance. Other objects and features will be in part apparent and in part pointed out hereinafter. Brief Description of the Drawings

Fig. 1 is a side elevation of orbital movement apparatus of the present invention;

Fig. 2 is a right side elevation of Fig. 1; Fig. 3 is a section taken along line 3--3 of Fig. 2 ;

Fig. 4 is an enlarged portion of Fig. 3 illustrating details; Fig. 5 is a side elevation of a hand sander incorporating the orbital movement apparatus of the present invention, parts being broken away for purposes of clarity; Fig. 6 is a horizontal section take along line

6--6 of Fig. 5;

Fig. 7 is a sectional view of a speed reduction unit incorporating the orbital movement apparatus of the present invention; and Fig. 8 is a vertical section taken along line

8--8 of Fig. 7.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. Description of Preferred Embodiments

Referring now to the drawings, Figs. 1-4 show an orbital movement mechanism or apparatus of the present invention in its most basic form and without reference to any specific mechanical application. This mechanism, which is designated in its entirety by the reference numeral 1, is shown as comprising first (left) and second (right) members designated 3 and 5, respectively, a shaft 7 journalled in a bearing 9 on the first member for rotation about an axis AX1, and an eccentric 11 at the outer (right as viewed in Fig. 4) end of the shaft. The eccentric, which is integrally formed with the shaft and journalled in a bearing 13 in member 5, has a central axis AX2 generally parallel to but radially offset a predetermined distance E from the axis AX1 of shaft 7. This distance E may be referred to as the "eccentricity" of eccentric 11. It will be noted that when shaft 7 rotates, a point on axis AX2 traces a circle having a diameter equal to twice the "eccentricity" of the eccentric. This may be referred to as the "throw" of eccentric 11, which is represented by the reference characters TH in Fig. 4. The members 3, 5 have opposing generally planar surfaces indicated at 15 and 17, respectively, disposed generally parallel to and face-to-face with one another. In accordance with this invention, members 3, 5 are coupled in such a way as to permit orbital movement while preventing rotational movement of member 5 with respect to member 3 upon relative rotation between shaft 7 and member 5. More specifically, members 3 and 5 have three connections therebetween, each of which is indicated generally at 19. Each connection comprises a pair of opposing recesses 21 in the planar surfaces 15, 17 of the two members 3, 5. These recesses are generally concave, circular in shape (as viewed in Fig. 2) and substantially identical in size with the central axis AX3 of one recess of each pair of opposing recesses being substantially parallel to and offset from the central axis AX4 of the other recess of the pair by distance E, the same distance as that between axes AX1 and AX2 of shaft 7 and eccentric 11 (see (Fig. 4). Each connection 19 also includes a ball 23 of suitably durable material (e.g., metal) in each pair of recesses 21, the combined depths of the opposing recesses being less than the diameter of the ball for maintaining, the planar surfaces 15, 17 of members 3, 5 spaced apart. The right member 5 is held on eccentric 11 by means of a circular retainer 25 secured, as by a screw 27, to the right end of the eccentric.

As best illustrated in Fig. 4, the opposing recesses 21 of each connection 19 are larger in diameter than the ball 23 and provide circular races for the ball during relative rotation between the left member 3 and shaft 7. During such relative rotation, the ball rolls around the inwardly rounded peripheral walls of the recesses 21, thereby permitting orbital movement, while at the same time preventing rotational movement, of the right member 5 with respect to the left member 3. The ball and recesses of each connection are so sized and dimensioned with respect to one another that during orbital movement of the right member with respect to the left member the center C of the ball traces a circle with respect to each recess having a diameter D substantially equal to the distance E, or the "eccentricity" of eccentric 11; and since the central axes AX3, AX4 of the two recesses are radially offset by the distance E, the right member is permitted to orbit with respect to the left member to the extent that, a point on the right member traces a circle with respect to the left member having a diameter approximately equal to 2E, or the "throw" of eccentric 11. This is in sharp contrast to the prior art orbital movement mechanism of the type involving the use of pin-mounted rollers projecting from one member through holes in another. While this prior art mechanism allows the same degree of orbital movement between respective mechanical parts, a point on a roller traces a circle having a diameter equal to twice the "eccentricity" (or the "throw") of the eccentric, with the diameter of a hole being equal to the diameter of the roller plus twice the eccentricity of the eccentric, whereas in the present invention the center C of the ball 23 traces a circle having a diameter D substantially equal to the eccentricity E of eccentric 11, with the diameter of the circular race or path around which the ball 23 rolls in each recess 21 being substantially equal to the diameter of the ball plus only one magnitude of eccentricity. Each recess 21 is preferably generally hemispherical in shape, with the inwardly rounded peripheral walls of the recess having a radius of curvature only slightly greater than the radius of curvature of the external surface of the ball. This ensures a rolling line contact between the ball, and the recess walls to minimize frictional losses. A pocket 29 in the bottom of each recess ensures that the ball 23 rolls freely therein. Thus, the only contact the ball makes as it rolls around each recess is a rolling line contact with the inwardly rounded wall of the recess.

While at least three connections 19 between members 3 and 5 are necessary to maintain opposing planar surfaces 15 and 17 generally parallel, it will be understood that the orbital movement mechanism will function properly with more than three connections. No matter what the number, however, the connections should be spaced substantially equidis tantly (e.g., every 120° with three connections) around shaft 7 for purposes of achieving a uniform load distribution over the connections.

It will also be understood that any number of input shafts 7 and eccentrics 11 can be employed to orbitally drive member 5, so long as each eccentric has the same "eccentricity" and "throw". Figs. 5 and 6 illustrate one possible practical application of the orbital movement mechanism 1 of Figs. 1-4. More specifically, the mechanism is shown incorporated in an orbital hand Sander, generally designated 31. As shown, the sander comprises a frame or housing 33 formed with a handle 35 for manipulation of the housing by hand, and a rectangular platen member 37 at the bottom of the housing, which is open. Attached to the bottom face of this platen is a piece of sandpaper 39, constituting working means, or, more specifically, abrading means. A pad 41 of suitably resilient material is sandwiched between the sandpaper and the platen member for evenly distributing the load over the surface being The sander further comprises drive means, generally indicated at 43, within the housing 33 for effecting orbital movement of the platen member with respect to the housing. Drive means 43 comprises an electric motor 45 having a vertically disposed output shaft 47, the lower end of which is in the form of a pinion gear interengaged with the hor izon tal spur gear 49 to provide reduced rota t ional drive to a shaft 51 journalled in a bearing 53 for rotation about a vertical axis AX5, bearing 53 being mounted in housing 33. An eccentric 55 is press-f i tted on the lower end of shaft 51 and has a central vertical axis AX6 radially offset a predetermined distance E from the central vertical axis AX5 of shaft 51. The eccentric is press-fitted into the inrfer race of a bearing 57, the outer race of which is press-fitted into a bearing support 58 which is suitably attached to platen member 37. This arrangement couples the eccentric to the platen member while permitting relative rotation therebetween. Other arrangements may also be suitable. Eccentric 55 is formed with an integral counterbalance 59 to offset the imbalance induced by the orbital motion of platen member 37.

In accordance with this invention, the platen member 37 and the housing 33 of the sander are connected to permit orbital movement, while at the same time preventing rotational movement, of the platen member with respect to the housing. More specifically, four squaresection posts, each designated 61, extend upwardly from the rectangular platen member 37 at the corners thereof toward four opposing posts, also designated 61, within the housing 33. The two posts of each pair of posts have opposing generally planar outer end faces and are connected, as indicated generally at 63, in the same manner described above in Figs. 1-4, that is, by a metal ball 65 received in a pair of opposing recesses 67 in the opposing outer end faces of posts 61, the recesses being radially offset a distance equal to the eccentricity E of eccentric 55. The relative sizes and dimensions of the ball 65 and r eces ses 67 are the same as described above with respect to the connections 19 of Figs. 1-4. To prevent the connections 63 from becoming contaminated with dust particles, etc., a seal (constituting seal means) in the form of a flexible sleeve 59 is fitted around the ends of each pair of opposing posts and extends between the posts for sealing the gap therebetween. This sleeve may be of any suitably durable material, such as rubber. It will be apparent from the above denseription that on energization of motor 45 output shaft 47 is driven to rotate vertical shaft 51 and eccentric 55, causing the platen member 37 to orbit, without rotating, relative to housing 33 of the sander. During this orbital movement, a point on the platen member traces a circle with respect to the housing, the circle having a diameter equal to twice the eccentricity E of eccentric 55. Since the housing and platen member are positively connected by connections 63 at the periphery of the platen member, continuous and uniform orbital movement of all peripheral portions of the platen .member is assured, even when uneven loads are applied to the platen member during sanding operations.

A device similar to sander 31 could be used for a variety of purposes, such as mixing, polishing, scrubbing, massaging, lapping, etc. Figs. 7 and 8 illustrate the mechanical movement mechanism 1 of Figs. 1-4 incorporated into a speedreduction unit (i.e., a speed reducer) generally designated 71. This unit comprises a base 73 and a cylindrical support member or housing 75 on the base, the right end of the housing 75 being closed by a circular end plate 77 and its left end by a circular end head 79. The unit also includes input and output shafts designated 81 and 83, respectively, and a motor 85 (constituting drive means) for rotating the input shaft. As shown, the left end of input shaft 81 is journalled in a thrust bearing 87 in the end head 79 for rotation about a generally horizontal axis AX7, and the right end of the shaft is journalled in a bearing 93 mounted within a recess 95 in the left end of output shaft 83. The latter shaft 83 is journalled in a pair of bearings 89, 91 in the right end of housing 75 for rotation about a generally horizontal axis coincident with axis- AX7 of input shaft 81. Of course, the axes of these two shafts 81, 83 are necessarily coincident inasmuch as the input shaft 81 is journalled in output shaft 83. It will be understood, however, that the input shaft can be supported independently of the output shaft and without being journalled therein. In such cases, the axes of the two shafts could be radially offset. The output shaft has an annular torque plate 97 bolted thereto at its left end.

The input shaft 81 is formed with an eccentric 99 thereon having a central axis AX8 generally parallel to but radially offset a predetermined distance E from axis AX7 of the input shaft. Eccentric 99 is journalled in a thrust bearing 101 mounted on a circular drive member in the form of a gear wheel 103 having teeth T at i ts outer periphery. A circular driven member in the form of a ring gear 105 secured to torque plate 97 is disposed around gear wheel 103, the ring gear having teeth T at its inner periphery interengageable with the teeth on the gear wheel thereby to effect conjoint movement of the two parts in a manner to be described in more detail hereinafter. The teeth T on the ring gear 105 and gear wheel 103 are identical in size and shape, and the two parts are so sized and dimensioned with respect to one another that the diameter of the pitch circle PC1 of the teeth on the gear wheel 103 is less than the diameter of the pitch circle PC2 of the teeth on the ring gear 105 by an amount equal to the "throw" of eccentric 99 (i.e., 2E). A counterbalance 107 on the input shaft 81 compensates for the off-center weight of gear wheel 103. As shown best in Fig. 7, the left face of the gear wheel 103 and the right face of end head 79 are generally planar and disposed substantially parallel to and face-to-face with one another. A plurality (e.g., six) of ball-and-socket connections 109 (identical to connections 19 in Figs. 1-4) between these opposing faces interconnect the end head and gear wheel. The connections 109 are disposed at regular angular intervals around the input shaft (e.g., every 60° with six connections). Each connection comprises a ball 111 received in a pair of recesses 113 in the opposing faces of end head 79 and gear wheel 103, the central axes of the recesses being radially offset a distance equal to the eccentricity E of eccentric 99. The relative sizes and dimensions of the ball and recesses of each connection 109 are the same as described above with respect to connections 19. The connections 109 permit orbital movement, while preventing rotational movement, of the gear wheel 103 with respect to the housing 75 of the reduction unit 71. The opposing faces of gear wheel 103 and end head 79 are maintained spaced apart a set distance by balls 111 of connections 109, and retained in contact with, balls 111 by a nut 115 threaded on the input shaft 81 up against a seal ring 117 disposed around the input shaft at the left side of thrust bearing 87. When this nut 115 is tightened, it tends to draw the input shaft 81 and thus thrust bearing 101 and gear wheel 103 leftwardly.

In operation, motor 85 drives the input shaft 81 at a first speed, causing eccentric 99 to rotate at the same speed with respect to gear wheel 103. This in turn causes the gear wheel to orbit with respect to the housing 75 of the reduction unit and also with respect to ring gear 105. Rotational movement of the gear wheel with respect to the ring gear is prevented by the connections 109 between the gear wheel and the end head 79 of the housing. As the gear wheel 103 orbits inside the ring gear 105, the teeth T on the gear wheel successively mesh with the teeth T of the ring gear, the net result being that the ring gear (and thus the output shaft 83) is advanced in the direction of rotation of the input shaft by an amount equal to the difference between the circumferences of pitch circles PC1 and PC2. This difference is directly proportional to the difference of the number of teeth on the gear wheel and ring gear. For example, if the gear wheel 103 is provided with 34 teeth and the ring gear 105 with 35 teeth, one rotation of the input shaft 81 (and thus one orbit of gear wheel 103) will advance the ring gear 105 a distance corresponding to the circular pitch of one tooth, thereby effecting a 35-1 speed reduction from the input shaft to the output shaft. Thus if the input shaft is driven at 350 rpm, the speed of the output shaft 83 will be reduced to 10 rpm. Very large step-down ratios may be achieved by placing one or more speed reduction units in series.

Gear wheel 103 and ring gear 105 could take other forms and accomplish the same result. For example, the teeth T on the two parts 103, 105, could be eliminated and replaced by circular tractional surfaces, with the. frictional contact between the wheel and the ring, as the wheel orbits, effecting rotation of the ring (and thus the output shaft 83) at a speed less than the speed of the input shaft. In this regard, for each rotation of the input shaft 81, the ring would be advanced by an amount equal to the difference between the outer circumference of the wheel and the inner circumference of the ring. A chain-and-sprocket combination could also be substituted for gear wheel 103 and ring gear 105, with the sprocket orbiting with respect to the chain and successively engaging the links of the chain to advance it for driving the output shaft at a reduced speed.

It will be observed that speed-reduction unit 71 can be effective as a speed increaser by driving shaft 83 instead of shaft 81, the latter of which would then be the output or takeoff shaft of the unit. In such a case, rotation of shaft 83, and thus of ring gear 105, would cause the gear wheel 103 to be driven orbitally, which would effect rotation of shaft 81 at a speed greater than the input speed of shaft 83. In the speed-reduction unit shown in Figs. 7 and 8, the rotation of the input shaft 81 in one direction results in the rotation of the output shaft 83 in the same direction, albeit at a reduced speed (1/35 the speed of the input shaft in the example used above). This is because the gear wheel 103 (a drive member) is disposed inside the ring gear 105 (a driven member). If this orientation were reversed, that is, if the drive member were disposed around the outside of the driven member, the driven member and output shaft would be rotated in a direction opposite to that of the input shaft, and at a somewhat different reduced speed (1/34 the speed of the input shaft in the example used above).

The present invention is also useful in direct drive units having a single input drive shaft but a plurality of output or takeoff shafts. using the reduction unit 71 shown in Figs. 7 and 8 as a reference, a direct drive unit with multiple takeoffs could be constructed simply by eliminating the driven member (e.g., ring gear 105 and torque wheel 97) and directly connecting the orbital drive member (e.g., gear wheel 103) and the output shaft by means of an eccentric identical to eccentric 99 connecting the input shaft and the drive member. This would provide direct drive for the output shaft. Additional output or takeoff shafts could also be coupled to the orbital drive member (e.g., gear wheel 103) in the same manner, that is, by means of eccentrics having an eccentricity E equal to that of eccentric 99.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Claims

ClaimsWHAT IS CLAIMED IS:

1. Orbital movement apparatus comprising first and second members, a shaft journalled in the first member, an eccentric on the shaft having an axis generally parallel to but radially offset a predetermined distance from the axis of the shaft, said eccentric being journalled in said second member, said members having opposing generally planar surfaces disposed generally parallel to and face-to-face with one another, and means for coupling said members to permit orbital movement while preventing rotational movement of the second member with respect to the first member upon relative rotation between the shaft and the first member, said coupling means comprising at least three connections between said members, each connection comprising a pair of opposing recesses in the planar surfaces of said members, said recesses being concave, generally circular in shape and substantially identical in size with the central axis of one recess of each pair being substantially parallel to and offset from the central axis of the other recess of the pair by said predetermined distance, and a ball in each said pair of recesses, the combined depths of said opposing recesses being less than the diameter of the ball for maintaining said planar surfaces spaced apart, said opposing recesses of each pair having inwardly rounded peripheral walls providing circular races for the respective ball whereby on relative rotation between said first member, and the shaft the ball rolls around said races with the center of the ball tracing a circle having a diameter approximately equal to said predetermined distance thereby permitting orbital movement while preventing rotational movement of the second member with respect to the first member, said orbital movement being such that a point on the second member traces a circle with respect to the first member, the diameter of the latter circle being approximately equal to twice said predetermined distance, each recess of said pair of opposing recesses being so sized and shaped relative to the ball therein that the only contact the ball makes as it rolls around the recesses is with the inwardly rounded walls of the recesses, the rounded wall of each recess having a radius of curvature somewhat greater than the radius of curvature of the ball thereby to ensure that the only contact between the ball and the recess wall is a rolling line contact to minimize frictional losses.

2. Orbital movement apparatus as set forth in claim 1 wherein the peripheral wall of each recess of said pair of opposing recesses has a radius of curvature only slightly greater than the radius of curvature of said ball.

3. Orbital movement apparatus as set forth in claim 1 wherein said first member comprises a frame and said second member comprises a platen member movable with respect to the frame, said apparatus further comprising drive means for rotating the shaft to effect orbital movement of the platen member with respect to the frame.

4. Orbital movement apparatus as set forth in claim 3 wherein said frame has a handle for facilitating manipulation of said apparatus, and said platen member has working means thereon.

5. Orbital movement apparatus as set forth in claim 4 wherein said working means comprises abrading means.

6. Orbital movement apparatus as set forth in claim 5 wherein said apparatus is a sander and said

7. Orbital movement apparatus as set forth in claim 3 wherein said connections between said frame and said platen member are generally adjacent the periphery of the platen member.

8. Orbital movement apparatus as set forth in claim 7 further comprising seal means around said connections.

9. Orbital movement apparatus as set forth in claim 8 wherein said frame and said platen member have at least three pairs of opposing posts thereon, each post having an outer end face, the opposing outer end faces of the two posts of each pair of opposing posts constituting said opposing generally planar surfaces having said pair of recesses therein, said seal means comprising a flexible sleeve fitted around the ends of each pair of opposing posts and extending therebetween for sealing the gap between the posts.

10. Orbital movement apparatus as set forth in claim 1 further comprising seal means around said connections.

11. Orbital movement apparatus as set forth in claim 10 wherein said seal means comprises a separate seal around each connection.

12. Orbital movement apparatus as set forth in claim 1 wherein said first member comprises a support member and said second member comprises a wheel movable with respect to the support member, said apparatus further comprising a circular member mounted for rotation with respect to said support member, said circular member and said wheel being interengageable for conjoint movement with the circular member being adapted to rotate as the wheel orbits with respect to said support member, and drive means for rotating either said shaft or said circular member at a first speed thereby to effect said conjoint movement whereby the other of said shaft and said circular member is rotated at a second speed different from said first speed.

13. Orbital movement apparatus as set forth in claim 12 wherein said circular member is disposed around said wheel for interengagement with the outer periphery of the wheel during orbital movement of the latter.

14. Orbital movement apparatus as set forth in claim 13 wherein said wheel is a gear wheel having teeth at its outer periphery and said circular member is a ring gear disposed around said gear wheel, said ring gear having teeth at its inner periphery interengageable with the teeth on the gear wheel.

15. Orbital movement apparatus as set forth in claim 12 wherein said circular member is mounted for rotation about an axis substantially coincident with the axis of said shaft.

16. Orbital movement apparatus as set forth in claim 12 wherein said drive means comprises a motor adapted to rotate said shaft at said first speed thereby to effect rotation of said circular member at said second speed, said second speed being less than said first speed.

17. Orbital movement apparatus as set forth in claim 1 wherein said first member comprises a support member, said second member comprises a drive member movable with respect to the support member, and said shaft constitutes an input shaft, said apparatus further comprising a driven member mounted for rotation with respect to said support member, said drive member being interengageable with the driven member during said orbital movement for rotating the driven member, and a motor for rotating said input shaft to effect said orbital movement of the drive member thereby to rotate the driven member.

18. Orbital movement apparatus as set forth in claim 17 wherein said drive member comprises a wheel and said driven member is disposed around the wheel for inter engagement with the outer periphery thereof during said orbital movement of the wheel.

19. Orbital movement apparatus as set forth in claim 18 wherein said wheel is a gear wheel having teeth at its outer periphery and said driven member is a ring gear disposed around the gear wheel, said ring gear having teeth at its inner periphery interengageable with the teeth on the gear wheel.

20. Orbital movement apparatus as set forth in claim 17 wherein said driven member is mounted for rotation about an axis substantially coincident with the axis of said input shaft.

21. Orbital movement apparatus comprising a frame having a handle for manipulation of the frame by hand, a platen member movable with respect to the frame, a shaft journalled in the frame, an eccentric on the shaft having an axis generally parallel to but radially offset a predetermined distance from the axis of the shaft, said eccentric being journalled in said platen member, said frame and platen member having opposing generally planar surfaces disposed generally parallel to and face-to-face with one another, means for coupling the frame and platen member to permit orbital movement while preventing rotational movement of the platen member with respect to the frame upon relative rotation between the shaft and the frame, said coupling means comprising at least three connections between the frame and said member, each connection comprising a pair of opposing recesses in said opposing planar surfaces, said recesses being generally circular in shape and substantially identical in size with the central axis of one recess of each pair being substantially parallel to and offset from the central axis of the other recess of the pair by said predetermined distance, and a ball in each said pair of recesses, the combined depths of said opposing recesses being less than the diameter of the ball for maintaining said planar surfaces spaced apart, said opposing recesses of each pair having peripheral walls providing circular races for the respective ball whereby on relative rotation between the frame and the shaft the ball rolls around said races with the center of the ball tracing a circle having a diameter approximately equal to said predetermined distance thereby permitting orbital movement while preventing rotational movement of the plat-en member with respect to the frame, said orbital movement being such that a point on the platen member traces a circle with respect to the frame, the diameter of the latter circle being approximately equal to twice said predetermined distance, and working means on the platen member engageable with a working surface during orbital movement of the platen member for working the surface as the frame is manipulated via said handle to traverse the surface.

22. Orbital movement apparatus as set forth in claim 21 wherein the peripheral wall of each recess of said pair of opposing recesses has a radius of curvature somewhat greater than the radius of curvature of said ball.

23. Orbital movement apparatus as set forth in claim 21 wherein said working means comprises abrading means.

24. Orbital movement apparatus as set forth in claim 23 wherein said apparatus is a sander and said abrading means comprises sandpaper.

25. Orbital movement apparatus as set forth in claim 21 wherein said connections between said frame and said platen member are generally adjacent the periphery of the platen member.

26. Orbital movement apparatus as set forth in claim 25 further comprising seal means around said connections.

27. Orbital movement apparatus as set forth in claim 26 wherein said frame and said platen member have at least three pairs of opposing posts thereon, each post having an outer end face, the opposing outer end faces of the two posts of each pair of opposing posts constituting said opposing generally planar surfaces having said pair of recesses therein, said seal means comprising a flexible sleeve fitted around the ends of each pair of opposing posts and extending therebetween for sealing the gap between the posts.

28. Orbital movement apparatus as set forth in claim 21 further comprising seal means around said connections.

29. Orbital movement apparatus as set forth in claim 28 wherein said seal means comprises a separate seal around each connection.