Speed varying device

A speed varying device comprises a box body for housing and supporting a set number of gear pairs kinematically connected to each other and to an input shaft and to an output shaft of the speed varying device itself; the box body is defined by a casing, presenting substantially the shape of a cup body and supporting a set number of gears kinematically connected to each other, and by a cover connectable to the casing to close the casing itself, supporting an additional set number of casings; to the cover is associated, or not, internally to the box body and in respective different embodiments of the speed varying device, a wall for supporting a part of the additional set number of gears.

BACKGROUND OF THE INVENTION
 The present invention relates to a speed varying device.
 In particular, the present invention relates to speed reducing device,
 whereto the description that follows shall refer without thereby losing
 its general nature.
 As is well known, speed reducers are mechanical devices provided with an
 input shaft and an output shaft, which are respectively connected to a
 motor and to a user unit and are able to drive the user unit itself with a
 rotatory motion presenting a lesser speed than the speed whereat the
 aforementioned input shaft rotates.
 Such types of reducers substantially comprise a box body for the
 containment of a plurality of shafts, whereon are splined gears which, in
 pairs, mutually transmit motion with appropriate transmission ratios and
 give rise to the aforementioned driving of the output shaft with lesser
 speed than that of the input shaft. The velocities of rotation of the
 input and, respectively, of the output shaft, as well as the value of the
 torque that the output shaft must transmit to the user unit, determine the
 choice of motor to be associated to each reducer, and oblige to provide
 the reducer itself with a number of gear pairs equal to or greater than
 two.
 In a first type of known reducer, when there is a need to obtain a total
 transmission ratio whose value entails the use of a number of gear pairs
 greater than two, it is necessary to interpose between a casing and a
 cover, comprised in the aforesaid box body, an additional sector of
 casing, which supports at least one pair of gears to be added to those
 already present. Similarly, the cover also needs to be chosen adequately
 as a function of the transmission ratio to be attained and of the
 aforementioned torque value, in order to allow coupling to the reducer a
 motor able to provide at its output a number of rotations per minute and a
 power suitable for the requirements.
 Obviously, the fact of having to construct and hold in stock an appropriate
 number both of additional covers and of casing sectors, differing from
 each other, entails a considerable financial burden. In addition, the fact
 that the aforementioned box body comprises the three aforesaid parts,
 mutually connected in pairs with interposition of sealing elements, such
 as respective gaskets for sealing lubricating fluids, entails considerable
 component complexity for the reducer described above, as well as a greater
 likelihood of seepage of the lubricant itself.
 In a second type of known reducers the casing is constructed in a single
 body, and it is fitted internally with an additional casing sector which
 is always present, both in the case of a reducer with two gear pairs, and
 in the case of a reducer with three or more gear pairs. Such additional
 casing sector essentially comprises a wall, provided with a number of
 holes or housings able to receive respective elements for supporting
 shafts whereon gears are splined. Such housings are in a sufficient number
 to accommodate the presence of the maximum number of gear pairs with which
 the reducers in question can be provided. Therefore, even when the reducer
 is provided with only two gear pairs, the aforesaid casing is fitted with
 an additional casing sector of considerable constructive complexity,
 provided with a number of housings exceeding the number actually necessary
 and characterized by a needlessly high cost of manufacture. Such cost of
 manufacture is particularly considerable also due to the fact that the
 mechanical complex constituted by the casing and by the aforementioned
 additional sector is obtained by casting, using a core of considerable
 size due to the presence in the complex itself of ample undercuts.
 Also known are reducers of the second type described wherein the
 aforementioned additional casing sector is manufactured separately from
 the aforesaid casing, and is connected thereto by means of screws or
 similar connecting means. In this case as well, the manufacturing and/or
 storage costs of the additional sector, which in case of utilization of
 two gear pairs is more complex than necessary, are quite burdensome.
 It should also be noted that, also in the previously described reducers
 fitted with an additional casing sector integral with the casing, it is
 necessary to be able to associate to the reducers themselves motors
 presenting different characteristics and able to accommodate the various
 needs. As a consequence of that fact it is necessary, as in the case of
 the first type of known reducer described above, to produce and stock a
 plurality of different types of covers suited to meet the various
 requirements.
 SUMMARY OF THE INVENTION
 The purpose of the present invention is therefore to eliminate the
 drawbacks mentioned above.
 The invention, as it is characterized by the claims, solves the problem of
 providing a speed reducing device, characterized in that it comprises a
 box body (59") for housing and supporting a set number of gear pairs
 varying as a function of the speed variation ratio of the device itself,
 said gear pairs being kinematically connected to each other to transmit
 the motion between an input shaft and an output shaft of said speed
 varying device; said box body being defined by a casing which is always
 the same for any set number of said gear pairs, and presenting
 substantially the form of a cup-shaped body and supporting a set number of
 said gears kinematically connected to each other; to said casing being
 connectable one of at least two covers chosen according to the set number
 of gears present in the speed varying device; each of said two covers
 supporting a further set number of said gears complementary to said set
 number of said gears present in said casing to form said desired variation
 ratio of said device, and at least to one of said two covers being
 associated, within said box body, a wall supporting a part of said further
 set number of gears, which is present only in the case of a pre-set body
 of said gear pairs and as a function of respective different versions of
 said speed varying device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 In FIG. 1, the number 1 indicates in its entirety a first type of reducer
 device known in the art, which comprises a box body 2 constituted by a
 casing 3, by an additional casing sector 4 and by a cover 5 mutually
 connected in pairs and in the order described above with interposition of
 sealing elements for the lubricating fluids not shown.
 In the description that follows reference shall be made to a plurality of
 axes constituting respective geometric entities of reference of respective
 mechanical details; such axes are all mutually parallel, and they are
 parallel to the directions of longitudinal development of the reducers
 which shall be described.
 The casing 3 is provided with a hole 6 with horizontal axis, obtained in
 one of its walls 7 positioned to the left in FIG. 1 and housing within it
 two ball bearings 8 supporting with their inner rings an output shaft 9
 with horizontal axis of the reducer 1, provided with an end portion
 projecting from the box body 2. On the other end of the shaft 9 is
 coaxially splined a gear wheel 10, which is engaged with a gear wheel 11
 splined (or obtained from the same piece) in correspondence with an
 intermediate portion of a tree 12 with horizontal axis. The end of the
 shaft 12 positioned to the left in FIG. 1 is housed inside the inner ring
 of a ball bearing 13 presenting its own outer ring fitted within a hole 14
 obtained in an internal position of the casing 3 located below the hole 6,
 while, to the side of the gear wheel 11, on the shaft 12 is coaxially
 splined a further gear wheel 15. The right-side end of the shaft 12 is
 housed inside the inner ring of a bearing 16, whose outer ring is fitted
 within a hole 17 with which the aforesaid additional casing sector 4 is
 provided.
 Such additional casing sector 4 is further provided, above the hole 17,
 with a hole 18 with horizontal axis within which is fitted the inner ring
 of a ball bearing 19 supporting coaxially with its inner ring a median
 portion of a shaft 20. On an end portion of such shaft 20 positioned to
 the left in FIG. 1 is splined (or obtained from the same piece) a gear
 wheel 21 able to engage, in use, with the aforementioned gear wheel 15,
 whilst immediately to the right of the bearing 19 the shaft 20 bears
 splined an additional gear wheel 22. The right end portion of the shaft 20
 is housed within the inner ring of a ball bearing 23, whose outer ring can
 be housed inside a cavity 24 present in the aforementioned cover 5.
 Inside a hole 25 of the cover 5, positioned below the cavity 24, are housed
 the outer rings of two ball bearings 26 and 27 coaxially set side by side,
 positioned respectively to the left and to the right in FIG. 1, whose
 inner rings are fitted around the respective areas of a shaft 28 with
 horizontal axis.
 On the end of shaft 28 positioned to the left in FIG. 1 is splined (or
 obtained from one piece) a gear wheel 29, able to co-operate, in use, with
 the aforementioned gear wheel 22.
 The right end of the shaft 28 is provided coaxially with a cavity 30 able
 to be engaged by the output shaft (not shown) of a motor that is not
 shown, which is connectable to a flange 31 comprised in the cover 5 by
 means of connecting elements constituted, for instance, by screws (not
 shown).
 The reducer 1 just described is provided with three pairs of gear wheels
 10, 11, 15, 21 and 22, 29, and it is of the first type described in the
 premises to the present description.
 As briefly mentioned, if in the reducer 1 in question only two pairs of
 gear wheels are to be used, it is necessary to replace both the additional
 casing sector 4, and the cover 5.
 FIGS. 2 and 3 show a reducer 32 of the second type described in the
 premises to the present description.
 Such reducer 32, of the type with two gear pairs, comprises a box body 33
 constituted by a casing 34, in turn constituted by a substantially
 cylindrical element 35 closed, in correspondence with its end positioned
 to the left in FIGS. 2 and 3, by a cover 36, and, in correspondence with
 its end positioned to the right, by a cover 37. The axial ends of the
 element 35 and the respective covers 36 and 37 are mutually connected with
 interposition of sealing gaskets not shown.
 The cover 36 is provided with a hole 38 with horizontal axis, housing
 within it a ball bearing 39 supporting with its inner ring an output shaft
 40 of the reducer 32 with horizontal axis, provided with an end portion
 projecting from the box body 33. On the other end of the shaft 40 is
 coaxially splined a gear wheel 41, which is engaged with a gear wheel 42
 splined (or obtained from the same piece) in correspondence with an
 intermediate portion of a shaft 43 with horizontal axis.
 As shown in FIGS. 2 and 3, the end of the shaft 43, positioned to the left
 in FIGS. 2 and 3, is housed within the inner ring of a ball bearing 44
 presenting its own outer ring fitted within a hole 45 obtained in an inner
 portion of the casing 34 located below the hole 38.
 As shown in FIG. 2, in proximity with the right side of the gear wheel 42,
 on the shaft 43 is fitted the inner ring of a ball bearing 46 whose outer
 ring is housed within a hole 47 obtained in a wall 48 which,
 perpendicularly to the axis of the shaft 40, transversely delimits an
 intermediate inner area of the casing 34.
 In such wall 48, above the hole 47, is present a hole 49 housing the outer
 ring of a ball bearing 50, whose inner ring is fitted coaxially to a right
 end portion of the aforementioned shaft 40.
 On the right end portion of the shaft 43 is splined coaxially a gear wheel
 51, which is engaged with a further gear wheel 52 splined on a left end
 portion of a shaft 53, which is supported in a rotating manner by means of
 two ball bearings 54 housed within a hole 55 obtained in the aforesaid
 cover 37.
 The right end of the shaft 53 is coaxially provided with a cavity 56 able
 to be engaged by the output shaft of a motor not shown herein, which is
 connectable to a flange 57 comprised in the cover 37 by means of
 connecting elements constituted, for instance, by screws (not shown).
 The reducer 32 just described is provided with two reduction stages
 constituted by two pairs of gear wheels 41, 42 and 51, 52, and, as
 specified above, it is of the second type considered in the premises of
 the present description.
 As mentioned, to the casing 34 of the reducer 32 is stably associated the
 aforesaid wall 48, better shown in the schematic FIG. 7, wherein are
 always present, although used only in part as in the case just described,
 the aforementioned holes 47 and 49 and an additional ground hole 58; the
 hole 58 is able to house possible means for supporting a third gear pair,
 and, as specified above, its presence, in the case of use of only two gear
 pairs, entails needlessly high costs to manufacture the casing 34 and, as
 a result, the entire reducer 32.
 Similarly to what is shown in FIG. 2, as shown in FIG. 3, in proximity to
 the right side of the gear wheel 42, the shaft 43 passes through a ground
 hole, not shown in FIG. 3 and obtained in a wall 48 which, perpendicularly
 to the axis of the shaft 40, transversely delimits an inner intermediate
 area of the casing 34. The hole through which the shaft 43 passes
 corresponds to the hole 58 of FIG. 5 and its wall 48 corresponds to the
 wall 48 of FIG. 2.
 To the right of the wall 48 of FIG. 3, on the shaft 43 is fitted the inner
 ring of a ball bearing 46 whose outer ring is housed within a hole 47
 obtained in a wall 110 with which the casing 34 is provided. To the right
 end of the shaft 43 of FIG. 3 is splined a gear wheel 51 which engages a
 further gear wheel 52 splined on a left end portion of a shaft 53, which
 is supported rotatorily by means of a ball bearing 54 housed inside a hole
 55 obtained in the aforesaid cover 37.
 In the case shown in FIG. 3 the shaft 53 can coincide with the output shaft
 of a motor not shown, which is connectable to the flange 57 comprised in
 the cover 37 by means of connecting elements known in the art and not
 shown.
 Similarly to the reducer 32 shown in FIG. 2, also the reducer 32 described
 above with reference to FIG. 3 is provided with two reduction stages
 constituted by two pairs of gear wheels 41, 42 and 51, 52, and, as
 specified above, it is of the second type considered in the premises of
 the present description.
 FIG. 4 shows the same reducer as in FIG. 3, but provided with three
 reduction stages. In particular the wall 48 is sectioned according to two
 different planes whereof one coincides with the section plane of FIG. 3
 and the other one is offset with respect to the axis of the shaft 40
 towards an observer looking at FIG. 4. This second section plane
 highlights that the wall 48 is provided, in addition to the aforementioned
 hole 49, with a further hole 111 which supports, by means of a bearing
 112, the right end of an additional shaft 113. The shaft 113 is provided,
 to the right of the hole 111, with a wheel 114 which enmeshes with a
 second wheel 115 obtained on the shaft 43.
 As shown in FIG. 4, the shaft 113 is driven by shaft 43 through the
 reduction pair constituted by the wheel 115 and by the wheel 114, and it
 is provided with a wheel 116 that enmeshes with the wheel 41. In
 particular the wheel 116 and the wheel 41 constitute an additional
 reduction stage. The reducer shown in FIG. 4 is thus provided with three
 reduction stages, constituted by the three pairs of gear wheels indicated,
 respectively with the numbers 51, 52, 114, 115, and 116, 41.
 Also in the case shown in FIG. 4, to the casing 34 of the reducer . 32 is
 stably associated the aforementioned wall 48, which in the case shown in
 FIG. 3 is identical to the one shown in FIG. 4, and in the case of FIG. 3
 relating to a reducer with two reduction stages, in wall 48 are still
 present, although used only partially as in the case just described, the
 aforementioned holes 47 and 49 and a further hole 111 shown only in FIG.
 4.
 Also in this additional case shown in FIGS. 3 and 4, the hole 111 is
 present both for the reducer with two reduction stages, and for the
 reducer with three reduction stages.
 FIGS. 6 and 7 respectively show two reducers 59 and 59' realized in
 accordance with the present invention, provided respectively with two and
 with three gear pairs.
 Both reducers 59 and 59' comprise a box body 59" defined by a casing 60
 having the shape of a cup body with the bottom located to the left in the
 figures in question, and which is always the same for any type of reducer,
 both in the case wherein the reducer presents two reduction stages, and in
 the case wherein the reducer presents three reduction stages. The inlet of
 such casing 60, positioned to the right in FIGS. 6 and 7, is closed by a
 cover comprised in the box body 59" and indicated respectively, in FIGS. 6
 and 7, with the numbers 61 and 62. Such covers 61 and 62, as shall become
 readily apparent hereafter, differ from each other.
 The casing 60 is provided with a hole 63 with horizontal axis, obtained in
 its wall 64 located to the left in FIGS. 6 and 7 and housing within it two
 ball bearings 65 supporting with their inner rings an output shaft 66 of
 the reducer 59, with horizontal axis, provided with an end portion
 projecting from the casing 60. On the other end of the shaft 66 is
 coaxially splined a gear wheel 67, which is engaged with a gear wheel 68
 splined (or obtained from one piece) in correspondence with an
 intermediate portion of a shaft 69 with horizontal axis. The end of the
 shaft 69 positioned to the left in FIGS. 6 and 7 is housed inside the
 inner ring of a ball bearing 70 presenting its own outer ring fit inside a
 hole 71 obtained in an inner portion of the casing 60 positioned below the
 hole 63, whilst, to the side of the gear wheel 68, on the shaft 69 is
 coaxially splined a further gear wheel 72. The right end of the shaft 69
 is housed inside the inner ring of a bearing 73, whose outer ring is
 fitted within a hole 74 obtained in a wall 75, 76, respectively delimiting
 the left side in the covers 61 and 62.
 As shown in FIG. 6, in a portion of the wall 75 overlying the hole 74 is
 obtained a further hole 77 with horizontal axis, within which is coaxially
 housed the outer ring of a ball bearing 78 whose function shall become
 readily apparent hereafter. An end of such hole 77 positioned to the right
 in FIG. 3 communicates with an inner cavity 79 of a sleeve 80 coaxial to
 the hole 77 itself and presenting its left end integral with the wall 75.
 Within the sleeve 80 is coaxially housed a ball bearing 81, which, in
 combination with the aforementioned bearing 78, supports in a rotatory
 manner a shaft 82 on whose end portions positioned within the casing 60
 and extending leftwards in FIG. 6 is splined (or obtained from the same
 piece) a gear wheel 83 able to co-operate with the aforementioned gear
 wheel 72.
 The right end of the shaft 82 is provided coaxially with a cavity 84 able
 to be engaged by the output shaft of a motor not shown herein, which is
 connectable to a flange 85, comprised in the cover 61 and connected to the
 right end of the sleeve 80, through connecting elements constituted, for
 instance, by screws 86.
 As shown in FIG. 7, the aforementioned wall 76 partially delimits the left
 flank of the cover 62 oriented towards the casing 60, and it is provided,
 in correspondence with its portion overlying the hole 74, with an
 additional hole 87 with horizontal axis, within which is coaxially housed
 the outer ring of a ball bearing 88 whose function shall become readily
 apparent hereafter. One end of such hole 87 positioned to the right in
 FIG. 7 communicates with a cavity 89 included between the wall 76 and a
 wall 90 defining the base, situated to the right of the wall 76 in FIG. 7,
 of a cup body 91 constituting substantially the body of the cover 62.
 An upper portion of the wall 90 is provided with a blind hole 92 coaxial to
 the aforementioned hole 87, within which is housed the outer ring of a
 ball bearing 93 which, in combination with the aforementioned bearing 88,
 supports in a rotatory manner a shaft 94 on whose median portion is
 splined a gear wheel 95. On the end portion of the shaft 94 positioned
 internally to the casing 60 and extending leftwards in FIG. 7 is splined
 (or obtained from the same piece) a gear wheel 96 able to co-operate with
 the aforementioned gear wheel 72.
 To the surface of the wall 90 positioned to the right, in FIG. 7, and
 oriented towards the exterior of the cover 62 is connected a sleeve 97
 developing along a horizontal axis and presenting its own left end
 integral with the wall 90 itself. The sleeve 97 is provided internally
 with a cavity 98 coaxial thereto, whose left end is coaxially adjacent to
 a hole 99 obtained in the wall 90. Within such hole 99 is coaxially housed
 a ball bearing 100, which co-operates with a ball bearing 101 housed
 coaxially within the sleeve 97 to support in a rotatory manner a shaft 102
 with horizontal axis, on whose end portion positioned internally to the
 casing 60 and extending leftwards in FIG. 7 is splined (or obtained from
 the same piece) a gear wheel 103 able to co-operate with the
 aforementioned gear wheel 95.
 The right end of the shaft 102 is provided coaxially with a cavity 104 able
 to be engaged by the output shaft of a motor not shown herein, which is
 connectable to a flange 105, comprised in the cover 62 and connected to
 the right end of the sleeve 97 through connecting elements constituted,
 for instance, by screws 106. The flanges 85 and 105 associated
 respectively to the covers 61 and 62, present such dimensions and shapes
 that they can be associated to the most suitable motor, respectively, for
 association to the reducer 59 of FIG. 3 or to the reducer 59' of FIG. 7.
 In particular, the flanges 85 and 105 present mutually different dimensions
 and/or conformation, in that, in the case wherein the wall 76 is present,
 as in the reducer 59' of FIG. 7, the motor (not shown) able to be
 associated to the reducer 59' shall preferably be less powerful, and hence
 smaller, for the same value of torque output by shaft 66, than the motor
 associated to the reducer 59.
 The reducers 59 and 59' represented in FIGS. 6 and 7 operate in a way known
 in itself, the motion being imparted to the reducers 59 and 59' themselves
 through the respective input shafts 82 and 102, and such motion being,
 respectively through the gear pairs 83, 72, 68, 67 and 103, 95, 96, 72,
 68, 67, transmitted to the respective output shafts 66.
 For the realization of the reducers 59 and 59', as stated, the same casing
 60 is used, with all the components contained therein, whilst it is
 sufficient to associate to the casing 60, respectively, the cover 61 or 62
 (with the elements associated thereto) to obtain the reducer 59 with two
 gear pairs or the reducer 59' with three gear pairs.
 From the above description it is evident that the reducers 59 and 59' fully
 attain the intended aim, since for their realization, in addition to the
 casing 60 and to the related internal components, common to both, it is
 sufficient to realize and keep in stock only the different types of covers
 (and the components associated thereto) able to meet the various
 requirements.
 Note that, thanks to their conformation, the reducers 59 and 59' described
 above present greater rigidity than the reducers realized in accordance
 with the prior art, and the complexes constituted by the casing 60 and by
 the covers 61, 62 thereto respectively and alternatively associated are
 able to guarantee an excellent seal to fluids, preventing the seepage of
 lubricating substances.
 The invention thus conceived can be subject to numerous modifications and
 variations without thereby departing from the scope of the inventive
 concept.
 For instance, the wall 76 may not constitute a part of the cover 62, and it
 may be connected to such cover 62 through connecting elements constituted,
 for instance, by screws.
 Lastly, it should be noted that all components described could be replaced
 with technically equivalent elements.