US2267362A - Dual wheel assembly - Google Patents

Description

Dec.'23, 1941. c. s. ASH

v DUAL WHEEL ASSEMBLY 5 Sheets-Sheet 2 Filed June 8, 1940 \(E NTOR Y 9 kw M ATTORNEYS Dec; 23, 1941. c. s. ASH

DUAL WHEEL AS SEMBLY 5 Sheets-Sheet 3 Filed June 8; 1940 o v Ill/k Dec.=23, 1941. c, s. ASH I 2,267,362

' DUAL WHEEL ASSEMBLY Filed June a, 1940 5 Sheets-Sheet 4 INVENTOR -De;23, 1941. 2 C.S.ASH 2,267,362

DUAL WHEEL ASSEMBLY Filed June 8, 1940 5 Sheets-Sheet 5 75 1;; NVENTOR 0 ATTORNEYS Patented Dec. 23,; '1941 DUAL WHEEL ASSEMBLY Charles s. Ash, Milford, Mich. Application June 8, 1940, Serial No. 339,420

14' Claims.

The present invention relates to new and useful improvements in dual wheel assemblies for use with automotive road vehicles.

Objects and advantagesof the invention will be set forth in part hereinafter and in part will be obvious herefrom, or may be learned by practice with the invention, the same being realized I p and attained by means of the instrumentalities and combinations pointed out in the appended claims.

The invention consists in the novel parts, constructions, arrangements, combinations and improvements herein shown and described.

The accompanying drawings, referred to herein and constituting a part hereof, illustrate one embodiment of the invention, and together with the description, serve to explain the principles of v the invention.

Of the drawings:

Figure l is an end elevation of a typical and illustrative embodiment of the present invention as applied-to a pair of dual wheels for an automotive roa'd vehicle, with means provided for driving and for braking the dual wheels, certain of the parts being broken away and. other parts being shown as a section taken on the line l-l of Figure 2; A

Figure 2 is 'a sectional view taken on the line 22 of Figure 1; Figure 3,is .a detailed side elevation of one of the parts of a modified illustrative embodiment of the present invention, with certain of its parts broken away;

Figure 4 is a central and verti al sectional view of the modification of the present invention em-,

. ploying the means of Figure 3, said sectional view corresponding to the section shown in Figure 2; a

Figure 5 is a sectional view taken on the line 5-5 of Figure 4 Figure 6 is a central vertical sectional view showing a further, modification of the present invention;

Figure '7 is a fragmentary sectional view taken on the line 1-1 of Figure 6;

Figure 8 is an arcuate section taken on the line 88 of Figure 6;

Figure 9 shows still another modification of the present invention and is a fragmentary radial section;

Figure 10 is a fragmentary sectional view. taken on the line I llll} of Figure 9; and

Figure 11 is a fragmentary arcuate taken on the line ill| of Figure 10.

The present invention has for its object the section provision of a novel and improved dual wheel assembly for automotive road vehicles havin independently rotatable, side by side wheels which may be driven or braked with equal torque and are held against excessive relative rotation. A further object of the invention is the provision of a driving and/or braking means acting upon a pair of independently rotatable side by side dual wheels through a differential gearing which substantially prevents opposite rotation of the wheels. Still another object of the invention is the provision of an improved bearing construction for independently rotatable dual wheels. The invention also provides a driving or braking means acting upon both of the independently rotatable dual wheels through a differential gearing in which a hydraulic fluid acts directly upon the differential gearing to prevent spinning of either of the wheels independently of the other. In accordance with the illustrative embodiments of the present invention, there are provided a pair of independently rotatable, side by side dual wheels mountedfor rotation on or about a common axis and drlvingly connected to a common drive shaft and/or a common braking means. Associated with the two wheels and the driving or braking means is a differential gear, one element of which is connected to the other wheel, while the other element is connected to the driv ing and/or braking means. For restraining excessive independent rotation of the dual wheels, as power or braking force is applled'to both of them through the differential, and to prevent the spinning of one wheel relatively to the other as might occur when the wheels have unequal driving or braking engagement with the road, hydraulic means directly associated with the' differentlal gearing is provided, and preferably these hydraulic means employ a lubricant as the hyis provided with a supply of viscous fluid such 7 as a heavy oil or grease which is displaced and moved circumferentlally within the chamber as the planets rotate during the independent rotadraulic medium so that the gears are constantly the two wheels are formed bearings ably support the sleeve 32 on the end of axle is offered to this independent rotation as the speed of one wheel increases with reference to the other; The outer adjacent faces of the hydraulic chamber are preferably provided with registering grooves into which an oil sealing member is introduced to prevent leakage from the chamber, and these adjacent faces are also preferably flnished to receive an annular thrust bearing between them. The pair'of dual wheels are preferably mounted side by side on a hub which is vrotatably mounted'upon an axle or axle housing, and in the illustrative embodiments a drive shaft is connected to this hub to transmit power to it and the brake drum is also connected to the hub for braking the dual wheels. This hub may also serve as the support for the spider on which the differential planets are mounted, and conveniently the entire differential gearing is positioned between the hub portions of the side byside dual wheels. In accordance with a modified embodiment of the invention, the differential planets are utias the impeller of a gear pump, and the space circumferentially between adjacent planets is provided with apertured obstructing members or baflles through which the grease or other viscous fluid is forced by the gears as the gears rotate due to the independent rotation of the wheels. a

While the invention is illustratlvely shown as applied to driven dual wheels, it is app icable to driven front or dirigible dual wheels-in which the ki pin is positioned between the two tires as in my prior Patent No. 1,979,598, dated November 6, 1934, and many features of the present ,invention are applicable to braked, undriven dual wheels such as are employed for trailing axles.

.,'It will be understood that the foregoing generaldescription'and the following detailed descriptio'nas well, are exemplary and explanatory of the invention but are not restrictive thereof. Referringnow in detail to the illustrative embodiment of the invention shown in Figures 1 and 2 of the accompanying drawings, the invention .is applied to a pair of side bysidewheels 23, 2| provided with'conventional tire rims 22 and 23, cured to their respective hubs 2i and 21 by means 'of the wheel mounting cap screws 23. Hubs 25 and21are preferably formed with a cylindrical interior forming a by-which the hubs 26 and 21 are rotatably journalled on a cylindrical sleeve 32. At its inner portion sleeve 32 34 and 35 in which are seated the tapered roller 31 and 33 which serve to freely rotatand these wheels are demountably se-' is provided with hearing seats motive vehicle projects outwardly beyond the end of the axle housing 40, and is provided with an integral flange which is'bolted to the end of sleeve 32 by screws 46, at the same time securing the interposed flange or washer 48.

Other means are provided for applying a braking forc to the sleeve 32 and for this purpose a brake drum 54 of conventional form and adapted to cooperate ,with conventional brake shoes which are not shown, is bolted to the inner radial flange 56 of the sleeve 32 by cap screws 51.

Thrust bearings are provided to permit'free rotation of the wheel hubs 26 and 21 on the sleeve 32, and for this purpose a thrust washer 60 is provided between the outer end of the hub 21 and the inner radial face of flange 48, and a similar thrust washer BI is provided between the inner end of th hub 26 and the outer radial face of flange 56, while the hubs 26 and 21 are spaced apart by means of the parallel radial faces'of the diflerential spider 64 which abuts the inner faces of the hubs 26 and 21.

A differential gearing is provided between the sleeve 32 and the wheel hubs 26 and 21, and as illustratively embodied this differential gearing comprises a pair of sun gears 10 and 1|, pinned by pins 13 to hubs 26 and 21, respectively, and a plurality of planetary bevel pinions 16 mounted on studs or dowels 11, which projectradially from the annular portion of 'spider 64, pinion 16 meshing with the sun gears 10 and 1|. Spider 64 is securely anchored to the sleeve 32 by means of cap screws 18 which project through it into tapped holes in. the inner web '19 of sleeve 32,

and thus prevent'movement of the studs 11 with respect to sleeve 32, axle shaft 44 and brake drum 54.

In order to provide for the lubrication of the diflerential gearing, and to provide the hydraulic checking means which restrains the wheels against rapid relative rotation as they are driven or braked, the sun gears 10 and 1| are each preferably mounted within facing annular recesses relatively long bearing surv face 23 within which are seated the' bushings 30 housing 40, and these hearings are held against bearin formed as an integral part of the wheel hubs 26 and 21. Radially beyond this hydraulic cham- 'ber formed by the recesses, the adjacent faces of hubs 26 and 21 are radial and in substantial contact with each other and are provided with cooperating registering circumferential grooves into which is compressed a felt sealing ring serving to prevent leakage of fluid from the chamber. Beyond the sealing ring 80, the radial faces of the hubs'26 and 21 are slightly recessed to provide bearing surfaces between which is received the ring-like thrust washer 82 of synthetic rubber or other suitable material which takes up the thrust between the two wheel members and .provides a further fluid seal. Means are provided for introducing lubricant into the fluid chamber 84 so that the supply therein may be maintained in the desired amount, and for this purpose one of the hubs is provided with a threaded hole into which is fitted a filler plug 35. A suitable dust cap 88 is provided over the outer end of the wheel hub 21, sleeve 32 and axle shaft flange 45 and may be retained on the wheel by means of cap screws 89.

. The hydraulic chamber is preferably of a size .to fit close to the outer peripheries of the sun gears 10, 1| and the convex outer face of pinions 15, thereby providing an annular cavity which minimizes the amount of lubricant required for both lubricating and checking the differential action of the pinions 16. -Thepinions bear against These metering apertures.

the outer periphery of the annular cavity which acts as a thrust surface holding the pinions against radial movement on their shafts.

In the operation of the illustrative embodiment, power is applied through the axle shaft M to the sleeve 32 to rotate it on its bearings 31! and 3d and thereby drive the ring 64 and the dowels or studs ill carrying the planetary pinions "it so as to drive ring gears and H and thereby rotate th wheels and 2!. Durviscous oil or grease in the hydraulic chamber moves with the gears it and II and the planets it and remains in a quiescent state, but as the planets revolve and rotate, the wheels move rel atively to each other and the planets move forwardly with respect to one wheel and rearwardly with respect to the other wheel, thereby displacing the entire body of lubricant and causing it to circulate within its chamber. This action resists relative rotation of the wheels and the faster this relative rotation the greater the resistance. In this way, spinning of either wheel is prevented and it is impossible for the vehicle to become stalled by reason of one wheel being in mud or oii the road as in all such cases a considerable amount of torqu can always 'be' applied to both wheels of each pair.

Similarly, in braking, the force is applied from the brake to sleeve 32 and through the dinerential to the, wheels,- and even if one wheel is off the ground or on an icy surface sufficient braking efiort may be applied to the other wheel of the pair.

In the embodiment shown in Figures 3, 4 and 5, the construction is generally similar to that shown in Figures 1 and 2, except that positive means are provided preventing the free flow oi oilor grease within the hydraulic chamber of the differential, thereby increasing the resistance to relative rapid independent rotation of the dual wheels.

As embodied, the spider 64a, carrying the planetary pinion stud 111 in the same manner as shown in Figures 1 and 2, is provided with radially extending baflles I00 having concave arcuate faces closely fitted to the cone generated by the rotation of the planetary gears 16, and a pair of these baffles-are provided on each side of each pinion 16 substantially filling the space between the bevel sun gears 10 and 1| and extending to the outer peripheral surface of the hydraulic chamber. Between the pair of baflles I00 on each side of each pinion 16, is provided a relatively wide radially extending aperture I03 which allows the heavy oil or grease to flow into the space between the pinion teeth, as the pinion 16 rotates. Each of the baiiles I00 is formed with a relatively small metering hole I05 which leads from the space between the baffles lOllon one side of one pinion 16 and the baffles Hill on the opposite side of an adjacent pinion and communicates with a point on the other side of the baffle which is closely adjacent to the point where the pinion teeth initially (or finally) engage with the teeth of the ring gear II! or II.

flow of lubricant so that "only a small quantity of lubricant can be-passed with a small force and a much greater force is required to pass even a slightly larger amount of lubricant. Thus, normal independent rotation of the wheels is substantially unimpeded while faster independent rotation or spinning of one wheel is almost impossible.

In the operation of the embodiment shown in Figures 3 to 5, assuming a clockwise rotation of the pinion It in Figure 5 which would correspond to the movement of the ring gear ii to the right while the ring-gear it is moving to the left or is being held still: Lubricant is delivered to the space between the teeth of pinion it through'each oi the two channels its, and this lubricant 'is moved clockwise by the movement of the pinion it. As the teeth of pinion it mesh with the 'ring gears it! and "it, the lubricant is displaced from between the teeth, it cannot escape to the left on gear it due to the fact that the gear teeth of gear ii are also filled with lubricant, and there is only a minimum clearance between the teeth of gear Til and the'adjacent face of the upper left bahe' itii.

Likewise, the lubricant cannot move counter clockwise over the face of the teeth of pinion it due to the small clearance between these teeth and the adjacent concave surface Wit. The only discharge port available for the lubricant is the metering aperture m5 and the lubricant escapes through this aperture into the main portion of the hydraulic chamber. The action of the metering aperture We in the lower right-hand baflie is exactly similar.

When the rotation of planet it is reversed, the action is similar but with the metering apertures its in the upper right and lower left-hand baiiie s Hill.

Figures 6 to 8 of the drawings illustrate a 'modification according to the present invention in which the space between adjacent planetary pinions it is baffled and is provided with arcuate box-like chambers which contain the lubricant.

In this embodiment the wheels and gearing may be substantially duplicates of those described above, but instead of the baffles Mil as shown in Figures 3 to 5, the space between the planets l6 and the gears 10 and II is filled by *arcuate, hollow box-like members i In which are substantially trapezoidal in cross-section. The annular portion of spider 64b is secured to the sleeve member 32 by means of the screws ii I which areprovided with projecting and slotted round The box-like members III! are hollow and provided with spaced parti-cylindrical walls H3 and H4. wall H3 being closely fitted to the outer surface of the spider 6412 while the outer surface of the outer wall H4 is closely fitted to the surface of the hydraulic chamber. At its'end each box-like member H0 is formed with concave walls HG which are closely fitted to the conical surface generated by the teeth of the planetary nion 6, and the remaining sides of the members H0 comprise walls H8 which are closely serve to restrict, the

fitted to the teeth of rin gears 10 and H. Projecting slightly beyond the ends of the box-like members I in are c rcumferentially extending beveled plates H9v which underlie the base of the bev l pinions I6.

The hollow box-like members H0 are provided with apertures to receive the heads of screws III. and with radially alined apertures I20 through which the screws Ill may be inserted and tightened, and these members H0 are se-- curely held in position due to the divergence in screws IIL' Apertures I23 are provided in the side walls H8 so that the lubricant may pass from the space between the teeth of gears I8 and II to the hollow interior of the members IIII, orvice versa, and other apertures I25 are provided centrally of the concave end walls Hi to communicate with the space between the teeth of pinion I6 and the hollow interior.

The degree of checking oi the independent rotation of the wheels is determined by the clear- I ance between the concave face IIS and the teeth side and up on the left-hand side of planetary pinion 16 into the mesh between the gears 10,

II and pinion I6, and at the same time lubricant is suppliedto the teeth of gears 10, II through the apertures I23. The lubricant displaced by the meshing of gears 10 and II with the pinion I6 must escape, and this flow is accomplished through the space between the gears III and II and the side walls H8, as well as through the space between the end wall IIS and the teeth of pinion I6. 4

In the embodiment shown in Figures '9 to 11, the construction is generally similar to that shown in Figs. 1 and 2 01' the drawings, except that the checking action on the independent rotation of the wheels is increased both by the use of bailles and by a supplementary gear pump actuated by the independent rotation of the wheels. As embodied, gear pump and baiiie assembly is mounted in the intervening space between one or more pairs of planetary pinions I6, and this assembly comprises an arcuate base I30 curved to fit the spider 84 and secured thereto by the spider mounting screws II.

Formed integrally with the base I33 is a pump body I32 in which is rotatably mounted a gear I34 meshing with one of the ring gears III or II and freely rotatable on stud I36. Extending circumferentially from each end of the pump body I32 are baiiie plates I 31 and I 33 which are closely fitted to the teeth of the ring gear and extend up to and almost contact with the teeth of the adjacent pinions 16. The pump body I3! is open on both sidesso that the teeth of the pump pinion I34 extend beyond it, thereby permitting the pinion I34 to mesh with the ring gear on one side and to communicate with the supply of lubricant in the hydraulic chamber on the other side. Metering apertures I are formed in the pump body to allow the discharge of lubricant under the pressure developed by the pump as the pinion I34 rotates in either direc- In this embodiment the independent rotation of the dual wheels is checked not only by the viscosity of the lubricant within the chamber as it is caused to flow by the normal action of the difierential pinions I6, but the independent rotation is also checked by the metering action of the ends of plates I31 and I38, where they abut the planetary pinions I6, and also the metering action of the apertures I4II as they restrict the flow of lubricant away from the mesh of pinion I34 and ring gears III and II, and by properly proportioning the clearances as well as the size of the apertures I40, and by a suitable.

choice of lubricant, any degree of checking may be obtained.

The invention in its broader aspects is not limited to the specific mechanisms shown and described but departures may be made therefrom within the scope of the accompanying claims without departing from the principles of the invention and without sacrificing its chief advantages.

' What I claim is:

- 1. In a dual wheeled assembly, a pair of side by side independently rotatable dual wheels, having adjacent circularly extending cavities cooperating to form a sealed hydraulic chamber and containing a viscous lubricant, a pair of sun gears, one secured to each wheel, spaced from each other and within said chamber, a sleeve aboutwhich the wheels are rotatable, a plurality of differential planetary pinions secured to said sleeve, meshing with said sun gears and displacing viscous lubricant within said chamber as they revolve, said chamber being closely fitted to the outer surfaces of the sun gears and pinions.

2. In a dual wheeled assembly, a pair of side by side independently rotatable dual wheels having adjacent circularly extending cavities with adjacent engaging faces of considerable area cooperating to form a sealed hydraulic chamber and containing a viscous. lubricant, a pair of sun gears, one secured to each wheel, spaced from each other and within said chamber, a sleeve about which the wheels are rotatable, a plurality of difierential planetary pinions secured to said sleeve, meshing with said sun gears and displacing viscous lubricant within said chamber as they revolve.

3. In a dual wheeled assembly, a pair of side by side independently rotatable dual wheels having adjacent circularly extending cavities with adjacent engaging faces of considerable area coi wheel, spaced from each other and within said chamber, a sleeve about which the wheels are rotatable, a plurality of differential planetary pinions secured to said sleeve, meshing with said sun gears and displacing viscous lubricant within said chamber as they revolve.

4. In a dual wheel assembly, a pair of side by side' independently rotatable dual wheels, a sleeve on which the wheels are joumalled, a circular member carried by the sleeve and spacing the wheels from each other, said wheels being formed with facing annular cavities adjacent said circular member to form an annular hydraulic chamber to contain a lubricant, a pair of sun gears, one within each cavity, a plurality of differential planetary pinions rotatably mounted on said circular memberand meshing with said sun gears to displace lubricant as they rotate whereby differential action of the gears is resisted and means for sealing said hydraulic chamber to prevent leakage therefrom.

5. In a dual wheeled assembly, a pair of side ing the wheels from each other,'said wheels hav-' ing adjacent engaging faces of considerable area and being formed with facing annular cavities adjacent said'circular member to form an annular hydraulic chamber to contain a lubricant, a pair of sun gears, one within each cavity, a plurality of differential planetary pinions rotatably mounted on said circular member and meshing with said sun gears to displace lubricant as they rotate whereby differential action of the gears is resisted and means for sealing said hydraulic chamber to prevent leakage therefrom.

6. In a dual wheeled assembly, a pair of side by side independently rotatable dual wheels; a sleeve on which the wheels are journalled, a circular member carried by the sleeve and spacing the wheels from each other, said wheels having adjacent engaging faces of considerable area and provided with a thrust bearing between them and being formed with facing annular cavities adjacent said circular member to form an annular hydraulic chamber to contain a lubricant, a pair of sun gears, one within each cavity, a plurality of mounted on said circular member and meshing difierential planetary pinions rotatably with-said sun gears to displace lubricant as they rotate whereby differential action of the gears is resisted and means for sealing said hydraulic chamber to prevent leakage therefrom.

7. In a dual wheeled assembly, a pair of side by side independently rotatable dual wheels having adjacent circularly extending cavities cooperating to form a sealed hydraulic chamber to contain a viscous lubricant, a pair of sun gears, one secured to each wheel, spaced from each gears and apertured to restrict the flow of lubricant induced by rotation of the pinions.

10. In a dual wheeled assembly, a pair of side by side independently rotatable dual wheels, a sleeve on which the wheels are journalled, a circular member carried by the sleeve and spacing the wheels from each other, said wheels being formed with facing annular cavities adjacent said circular member to form an annular hydraulic chamber to contain a lubricant, a pair of sun gears, one within each cavity, a plurality of differential planetary pinions rotatably mounted on said circular member and meshing ing the wheels from each other, said wheels other and within said chamber, a sleeve about which the wheels are rotatable, a plurality of differential planetary pinions secured to said sleeve, meshing with said sun gears and displacing viscous lubricant within said chamber as they revolve, and means adjacent the mesh of the pinions and gears for restricting the flow of lubricant to restrain independent rotation,

'said chamber being closely fitted to the outer surfaces of the sun gears and pinions.

8. In a dual wheeled assembly, a pair of side by side independently rotatable dual wheels having adjacent circularly extending cavities with adjacent engaging faces of considerable area cooperating to form a. sealed hydraulic chamber to contain a viscous lubricant, sealing means be-.

tween said faces to prevent leakage from said chamber and a thrust bearing between said faces, a pair of sun gears, one secured to each wheel,

- spaced from each other and within said chamber, a sleeve about which the wheels are rotatable, a plurality of differential planetary pinions secured to said sleeve, meshing with said sun gears and displacing viscous lubricant within said chamber as they revolve, and means adjacent the mesh of the'pinions and gears for restricting the flow of lubricant to restrain independent rotation. v

9. In a dual wheeled assembly, a pair of side by side independently rotatable dual wheels having adjacent circularly extending cavities with adjacent engaging faces of considerable area cooperating to form a sealed hydraulic chamber to contain a viscous lubricant, sealing'means between said faces to prevent leakage from said chamber and a thrust bearing between said faces, a pair of sun gears, one secured to each wheel, spaced from each other and within said chamber, a sleeve about whichthe wheels are rotatable, af-plurality of differential planetary pinions secured to said sleeve, meshing with said sun gears and displacing viscous lubricant within said chamber as they revolve, and baiile means xtending along the surface of the pinions and hollow box-like member substantially filling the chamber between adjacent planetary pinions and provided with apertures to allow lubricant to flow to the gears and pinions and to restrict flow of lubricant away from the gears and pinions.

11. In a dual wheeled assembly, a pair of side by side independently rotatable dual wheels, a sleeve on which the wheels are journalled, a circular member carried by the sleeve and spactatably mounted on said circular member and meshing with said. sun gears to displace lubricant as they rotate whereby differential action of the gears is resisted, means for sealing said hydraulic chamber to prevent leakage therefrom, and a hollow box-like" member substantially filling the chamber between adjacent planetary pinions and provided with apertures to allow lubricant to flow to the gears and pinions and to restrict flow of lubricant away from the gears and pinions.

12. In a dual wheeled assembly, a pair of side by side independently rotatable dual wheels, a sleeve on which the wheels are journalled, a circular member carried by the sleeve and spacing the wheels from each other, said wheels having adjacent engaging faces of considerable area and provided with a. thrust bearing between them and being formed with facing annular cavities adjacent said circular member to form an annular hydraulic chamber to contain a lubricant, a pair of sun gears, one within each cavity, a plurality of differential planetary pinions rotatably mounted on said circular member and meshing with said 'sun gears to displace lubricant as they rotate whereby differential action of the-gears is resisted, means for sealing said hydraulic chamber to prevent leakage therelarhydraulic chamber and containing a viscous lubricant, a pair of sun gears, one secured to each wheel hub, spaced from each other and within said chamber, a sleeve about which the wheel hubs are rotatable, and having radially extending studs between the wheel hub's, ditierential planetary plnions rotatable on the studs and meshing with the sun gears, said pinions having their outer faces bearing against the annular surface oi! the wheel hubs whereby the pinions are restrained against radial movement with respect to the sleeve.

14. In a dual wheeled assembly, the combination of a pair of independently rotatable dual wheel hubs, having adjacent circularly extending cavities cooperating to form a sealed hydraulic 10 her as they revolve.

chamber having an annular periphery and containing viscous lubricant, sun gears, one secured to each wheel hub, and within said chamber, a sleeve about which the wheel hubs are rotatable and having radial studs between the wheels and in said chamber, pinions on said studs meshing with the sun gears and bearing against the annular periphery of the chamber, said pinions displacing the viscous lubricant within the cham- CHARLES S. ASH.

Images