US3794122A

US3794122A - Snow conditioning machine

Info

Publication number: US3794122A
Application number: US00234512A
Authority: US
Inventors: D Rohrer
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-03-14
Filing date: 1972-03-14
Publication date: 1974-02-26
Anticipated expiration: 1991-02-26

Abstract

A snow conditioning machine for conditioning snow at ski areas to give it a proper texture for skiing even after it has become packed hard or become icy including a rotating member having radial teeth that intermesh with stationary teeth on the machine and through which the snow passes to be reduced in particle size to an acceptable level. The unit includes means for breaking hard packed snow into large chunks which are then passes into the intermeshing teeth of the rotating member and the stationary member. Support rollers for the unit are provided, this makes the unit usable for compacting newly fallen snow when the rotating member is not in use.

Description

limited States Patent [191 Rohrer [451 Feb. 26, 1974 1 SNOW CONDITIONING MACHINE [76] Inventor: Dennis L. Rohrer, 15400 Buck Hill Rd., Burnsville, Minn. 55378 [22] Filed: Mar. 14, 1972 [21] Appl. No.: 234,512

[56] References Cited UNITED STATES PATENTS 848,977 4/1907 Davis 172/174 2,394,017 2/1946 Seaman 172/68 X 1,278,795 9/1918 Uhan 172/146 2,607,176 8/1952 McVicar.... 172/148 2,675,748 4/1954 Patterson... 172/66 2,364,449 12/1944 Jones 172/66 X 281,149 7/1883 Smith 172/69 510,166 12/1893 Farmer 172/69 X 3,409,088 ll/1968 Lindbeck et a1 172/66 1,828,681 10/1931 Reinking 172/68 3,006,422 10/1961 Mighell 172/142 FOREIGN PATENTS OR APPLICATIONS 1,248,085 8/1967 Germany 172/122 1,195,996 10/1964 Germany 172/120 25,357 12/1919 Denmark 172/67 Primary Examiner-Emest T, Wright, Jr. Assistant Examiner-Eugene H. Eickholt Attorney, Agent, or Firm-Dugger, Johnson & Westman {57] ABSTRACT A snow conditioning machine for conditioning snow at ski areas to give it a proper texture for skiing even after it has become packed hard or become icy including a rotating member having radial teeth that intermesh with stationary teeth on the machine and through which the snow passes to be reduced in particle size. to an acceptable level. The unit includes means for breaking hard packed snow into large chunks which are then passes into the intermeshing teeth of the rotating member and the stationary member. Support rollers for the unit are provided, this makes the unit usable for compacting newly fallen snow when the rotating member is not in use.

18 Claims, 5 Drawing Figures SNOW CONDITIONING MACHINE BACKGROUND OF THE INVENTION are generally rotary hoes or spring tooth cultivators that are normally used for cultivating the earth or some combination of the two devices. Specialized equipment for grooming snow or conditioning snow for skiing is shown in U.S. Pat. No. 3,368,292 and U.S. Pat. No. 3,478,827.

A rotating earth working tool that conditions the ground, and reduces particle size or comminutes the ground is shown in the U.S. Patent to Staats, U.S. Pat. No. 2,785,613. A rotating flail type beater is shown for conditioning soil. Also, the Richey U.S. Pat. No. 2,667,022 shows a flail type device for shredding stalks ofa corn field or the like, and the U.S. Patent to Cohen, U.S. Pat. No. 3,008,526 shows a soil conditioning apparatus which utilizes three separate flail type beaters for engaging the soil with hammers for pulverizing soil.

Another form of a flail type device is shown in the MacDonald U.S. Pat. No. 2,986,841.

All of these earth working devices do not have the intermesh teeth for obtaining a desired particle size, and of course in the conditioning of snow it is important that the particle size be maintained at a relatively controlled level so that it isnt so far in that it packs immediately, and is not so coarse so that it interferes with proper skiing.

SUMMARY OF THE INVENTION The present invention relates to a snow conditioning or grooming apparatus which includes a rotating member (rotor) having radially extending teeth spaced along the transverse length thereof. Means are pro vided for moving a layer of snow into the path of the rotor teeth. As shown the teeth of the rotor intermesh with stationary teeth on a transverse bar that engages the snow. The bar pushes snow ahead of it so the upper 2-3 inches of snow has to go over the bar and into the rotor teeth. The snow conditioning machine also includes a spring tooth harrow type device for breaking up packed snow into usable chunks, which then pass over the transverse bar and through the intermeshing teeth of the unit.

The entire comminuting or pulverizing apparatus including the rotor having the radially extending teeth, and the transverse support or bar having the stationary teeth is mounted in a subframe assembly with a large flotation support roller. The subframe assembly is pivotally mounted to the main frame and can be tilted relative to the main frame of the unit so that the large rear roller is supporting the rear of the unit with the rotor and transverse bar spaced off the surface of the snow, or the subframe can be moved to a position wherein the transverse bar rides along the surface of the snow and the rear roller is spaced off the snow surface. The unit can be used as a snow compactor for compacting newly fallen snow when the rear roller is contacting the snow and the rotor is spaced from the snow.

A large roller rotatably mounted at the front of the main frame supports the unit without severly compacting the snow.

The intermeshing teeth of the rotor and transverse bar are made to be replaceable either in sections, or individually, so that if a foreign object passes through the teeth and one of the teeth breaks it can be replaced without completely changing the entire machine. The power unit for operating the machine components is mounted on the main frame. The machine is shown as a towed vehicle but it could also be self propelled, if desired.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side elevational view of the snow conditioning machine made according to the present invention;

FIG. 2 is a top plan view of the machine of FIG. 1;

FIG. 3 is a fragmentary side elevational view showing the snow conditioning machine in a position with a rear roller engaging the ground to support a snow comminutation rotor portion spaced from the snow;

FIG. 4 is a fragmentary front elevational view of the snow comminutation portion of the present invention;

FIG. 5 is a sectional view taken as on line 5-5 in FIG. 4;

DESCRIPTION OF THE PREFERRED EMBODIMENT A snow conditioningmachine illustrated generally at 10 includes a main frame assembly 11 that has a pair of longitudinally extending main

side frame members

12,12 joined together with a front cross member 13 and a center cross member 14, and any additional cross members that may be necessary to hold the frame ina rigid assembly for the loads encountered. The frame assembly 11 can be bolted together, or can be welded if desired within the requirements of being able to assemble the unit. The frame assembly 11 has a hitch pole 15 mounted to the front cross frame member thereof, and this hitch pole includes the usual clevis or other attaching means for connecting the unit to a towing vehicle such as the usual tractors that have large tracks for flotation over the snow.

A large flotation roller 20 is rotatably mounted on suitable bearings 2l at the foward end of the frame 11, and extends between the

side members

12,12. The rol ler 20 can be made of a hollow metal tube, such as of a conventional metal culvert approximately 30 inches in diameter, with discs 20A welded at the ends of the tube, and having stub shafts extending from the discs into the bearings 21. The roller will merely rotate and roll along the ground when the frame is pulled.

The frame has a support carriage 23 mounted adjacent the forward end, over the roller 20, that supports an internal combustion engine illustrated schematically at 24, and a hydraulic fluid reservoir R or the like. The engine 24 provides the power for operating powered components of the snow conditioning machine It). The engine 24 drives a hydraulic pump 25, which takes fluid from the fluid reservoir and pumps it under pressure to a valve assembly shown schematically at 26 that controls flow of fluid under pressure to the various components. The pump and valve can be mounted in any desired manner in order to obtain the power control necessary for operating the snow conditioning machine.

The control valve can be mounted on the towing vehicle, if desired.

The snow conditioning machine is thus supported by the forward roller 20. Immediately to the rear of the forward roller 20 there are a pair of cross shafts 28, each of which is square in cross section except at their ends, which are turned round and are rotatably mounted in suitable supports 29 at the

opposite frame members

12,12. The shafts 28 are used for mounting a plurality of conventional spring harrow teeth 31, that are mounted onto the shafts 28 with suitable U bolts or clamps, in a usual manner. Pivoting of shafts 28 is controlled through the use of a hydraulic cylinder 32 having an extendable and retractable rod 33. The rod 33 acts through a torque arm 34 attached to the rear shaft 28. A link 35 is pivotally connected to arm 34 and to an arm 35B mounted on the front shaft 28 so that when the rear shaft 28 is pivoted through movement of the torque arm 34, both shafts 28 will pivot. The harrow teeth 31 will be raised when the rod 33 is retracted and will be lowered into the snow when the rod 33 is extended as shown in FIG. 1. The harrow teeth are used for breaking up firmly packed snow, or icy snow into chunks that will be readily reduced in size when they pass through the snow comminution assembly.

The snow comminution assembly is part of a subframe illustrated generally at 40 and includes a large housing 41 that has a formed transverse top plate member 42 extending across the machine which has end plates 43 on the opposite ends thereof. The end plates 43 in turn rotatably support a toothed rotor indicated generally at 44 (see FIG. 4) that is rotatably mounted in suitable bearings 45 attached to the opposite end plates 43. The rotor 44 is made up of a central square tubular shaft 46 (see FIG. and at the ends of the shaft 46, round stub shafts 47 are welded in place for rotatable mounting in the bearings. Each of the shafts 47 has a threaded section 48 of larger diameter than the portions mounted in the bearings on which nuts 49 are threaded. The nuts 49 are securely locked in place with set screws to keep them from loosening once the rotor is assembled. The rotor is made up of a plurality blade like teeth assemblies indicated generally at 55. The rotor teeth assemblies, as perhaps best shown in FIGS. 4 and 5, have central hubs 56 that have square openings that slide over the square tube 46 and closely fit the tube and each tooth assembly has four radial blades or teeth indicated at 55A, 55B, 55C and 55D for the end tooth assembly shown in FIG. 5. The hubs 56 are welded to the actual tooth plate which is made from a plate having the four blades formed by cutting out portions of the plate and which are spaced 90 apart. The desired number of tooth assemblies are slid onto the square shaft 46 and are held on the shaft by the nuts 49 at each end of the shaft to form the rotor made up of individual tooth assemblies stacked together. The openings in hubs 56 are positioned so that some of the blades or teeth have a different angular position than blades of other tooth assemblies when mounted on the shaft. For example, as shown in FIG. 4, a series of identical tooth assemblies 57 are adjacent each other and then a stack of tooth assemblies 58 are mounted on the shaft 46. The blades of tooth assemblies 58 are angularly offset from the blades of tooth assemblies 57 by a desired amount, for example 15. The next stack of tooth assemblies 59 are offset another 15 to stagger the blades so the loads on the shaft when breaking up snow are equalized. If desired, adjacent teeth can be offset from each other so the blades actually spiral around the rotor rather than having several identically positioned blades in a row or stack. As shown, there are a plurality of rotor sections with the teeth in each section oriented identically, but which are annularly offset from the other adjacent sections.

The blade offset insures that the forces on the rotor are relatively balanced so that all of the blades dont contact snow at the same time and cause excessive loads on the rotor itself. The individual teeth or blades of the rotor assembly are spaced apart in axial direction of shaft 46 as shown in FIG. 4, and these spaces are approximately one half inch as shown. The hubs 56 provide for the spacing.

The snow conditioning machine is provided with a bottom snow engaging and feeding cross bar assembly 60 that supports a plurality of spaced triangular shaped upright teeth 61. The teeth 61 are attached as shown to individual U-shaped mounting sections 62 which fit onto the cross bar 60, and can be bolted in place. The sections 62 can be made up with any desired number of teeth 61 fixed thereto, for example sixteen teeth in a section. Then if any of the teeth 61 break out, the section 62 can be replaced. The teeth 61 may be made of a spring steel, and individually bolted or fastened directly in place onto the cross bar 60 with a suitable bracket, so that individual teeth 61 can be replaced if they break. The teeth 61 are triangular plate blades as shown and have uprightly extending edge portions facing in the direction of movement of the snow conditioning machine. The rotor blade teeth pass between two adjacent fixed teeth 61 to provide a breaking or grinding or comminuting action for any material that is engaged by these teeth.

The cross bar 60 can be attached between the end plates 43 in any desired manner, but should be removable. For example, end brackets 64 can be provided which bolt to the end plates 43, and which are welded to the cross bar. The cross bar 60 can be removed by removing of the cap screws holding the brackets 64. The end plates 43 are slotted from the bottom to permit the rotor and cross bar 60 to be removed. Braces 65 from the housing to the cross bar 60 can be provided if desired. The rotor teeth are spaced to miss the braces.

The bar 60 also may have edge mounted planar guide blades 60A welded to the bottom thereof. The blades 60A travel below the surface of the snow and stabilize the frame from lateral shifting.

The end plates 43 extend rearwardly even with the rear end of the top plate 42 of housing 41. A pair of side frame members 66 are attached to the side plates 43 so they move as part of the subframe 40. The side frame members 66 are provided with stub shafts 67 which are rotatably mounted in hubs 68 that are attached with brackets 68A to the main side frame members 12. The shafts 67 can be pinned at their outer ends (outside hubs 68) to keep the main frame members 12 from separating. The frame members 66 include rearwardly extending portions 69 that are angled upwardly and which are connected together with a rear cross piece 70. i

The frame portions 69 support bearings 71 that in turn rotatably mount stub shafts 72 fixed to the end plates of a support tube or roller 73. The support roller 73 is constructed similar to the roller 20, but the end discs 73A extend outwardly beyond the periphery of the roller a small amount to give the machine stability when the roller 73 is on the snow.

The pivoting of the subframe 46 which includes housing 41, and the roller 73, is controlled through use of a pair of hydraulic cylinders '75 that are attached at the first ends to brackets 75A on upright mast or arm members 7a which are fixed to the subframe member 66 and therefore fixed to the housing side plates 43. The hydraulic cylinders 75 have extendable and retractable rods 75C that are attached to brackets 75B fixed to side frame members 12. Movement of the cylinder rods 75C therefore determines the position of the subframe assembly about its pivot shaft. When the rods are retracted the cross bar 60 is riding on the snow and the roller 73 is off the snow, as shown in FIG. 1. However, by extending the rods of cylinders 75 under hydraulic pressures through controlling the valve 26, the entire housing 411 is lifted off the snow surface, and the roller 73 contacts the snow surface as the subframe pivots about the axis of the shafts 67. The roller 73 can be used for compacting the snow if desired.

The toothed rotor assembly 44 is driven with a hydraulic motor 80 that is mounted onto a bracket 81 adjustably attached to one of the end plates 43. The output shaft of motor 81 has a sprocket 82 drivably mounted thereon which in turn drives a chain 83 to drive a sprocket 84 on the corresponding end shaft 47 of the rotor. The hydraulic motor 80 is controlled through valve 26, (which has a sufficient member of individual valves for operating these hydraulic components), and when driven the motor will rotate the rotor in direction as indicated by the arrow 86, to cause the rotor teeth 55 to pass between the fixed teeth 61. Any snow that is in front of the lower teeth 61 will be pulverized or reduced in size by the intermeshing teeth on the rotating rotor. The bar 60 pushes snow ahead of it as shown in FlG. 5. As the frame is moved along the snow the rotor breaks the snow up and forces it through the fixed teeth fill. The size of the snow particles when it has passed through the interrneshing teeth will be approximately pea" size which is a good size for giving good control in skiing conditions, but is not so fine that it will readily pack again. The rotor is rotated at about 750 rpm with an outer diameter of teeth of about l2 inches.

Thus when the unit is to be used, the spring harrow teeth 31! are lowered into the snow by operating cylinder 32 and as the frame moves over the snow the harrow teeth break up the hard snow into chunks of mod erate size. Then the bar 60 pushes snow ahead of it as it moves along and the chunks and other snow will be engaged by the rotor assembly 44 and the teeth 55 thereof, and it will be comminuted or pulverized as the teeth 55 pass between the stationary teeth 61. The bar 60 rides along the surface of the snow, and insures that any loose snow is pushed up ahead of it, and has to pass through the intermeshing teeth from the rotor 44 and the stationary teeth at. The bar 60 actually forms a snow feeding means for feedingsnow into the rotor.

The bar 60 can have suitable central supports, if desired, as shown in FIG. d which support the bar from the housing plate 42 for added strength. Guide wings 90 are mounted ahead of the rotor housing to guide snow into the rotor from the sides and prevent ridges from forming. These guide wings are pivoted to the 7 substituted and the rotor reassembled.

The pivoting subassembly controlled by hydraulic cylinders make the unit easy to operate and give it dual usage. The rotor housing assembly is of sufficient weight so that it will ride firmly on the snow. The bar 60 is supported by the snow slightly below the surface of the snow so that chunks and loose snow are pushed ahead of the bar and then pass into the rotor.

The use of the harrow teeth for breaking the snow up into chunks which will pass through the rotor insures that an adequate job of pulverization or snow grooming is achieved.

The configuration of the corrugated culvert rollers is shown only partially in FIG. 2. Both rollers are made of the corrugated material, because when used for compacting snow the small, gentle ridges left make a better skiing surface than a smooth roller.

The carriage or frame 23 is supported an the side frame members 12 and has cross members extending above roller 20 all the way across the frame to support the engine and other components. There are also fore and aft braces 23A extending from cross member 1141 to the carriage cross members, and braces 238 from the front cross member to the carriage for strengthening purposes. One end of cylinder 32 is mounted on a bracket connected to braces 23A.

It should also be noted that the rear portion of the top plate 42 serves to deflect snow thrown rearwardly by the rotor to cause the pulverized snow to drop back down onto the snow into an even layer and form a new skiing surface.

What is claimed is:

l. A snow conditioning apparatus comprising a vehi cle having a main frame adapted to be moved over the surface of snow including front support means at a front portion of the vehicle, and a subframe assembly pivotally mounted to said main frame to the rear of said front support means, rear support means mounted on said subframe assembly at the rear of said vehicle, a snow conditioning section mounted on said subframe assembly comprising a rotor, means to rotatably mount said rotor to said subframe assembly about an axis substantially transverse to the direction of movement of said vehicle, said rotor including a plurality of axially spaced radially extending rotor teeth along the axial length thereof, power means to rotate said rotor at a desired speed to comminute snow coming in contact with said teeth as the rotor is rotated, a transverse support and feed bar member narrow in front and rear direction, means to mount said feed bar member on said subframe assembly in fixed position with respect to said rotor and below said rotor, said rear support means being mounted to said subframe assembly rearwardly of said rotor in direction of normal movement and on the opposite side of the pivotal mounting of the subframe assembly to the main frame from said rotor, power means to pivot said subframe assembly about its pivotal mounting to said main frame to selectively move said rotor away from said snow and support the rear portions of said main frame on said rear support means, and alternately to lift said rear support means from said snow and move said feed bar member into engagement with said snow to push snow toward said rotor as said vehicle is moved while supported by the SHOW.

2. The combination specified in claim 1 and a plurality of upright teeth mounted on said feed bar member and positioned to pass between the radially extending teeth of said rotor, whereby snow engaged by said feed bar member is contacted by said rotor teeth and forced between said upright teeth by the teeth of said rotor.

3. The combination specified in claim 2 and removable means for mounting the upright teeth to said feed bar member.

4. The combination specified in claim 2 wherein said rotor has a central shaft, and said rotor teeth comprise individual axially narrow tooth assemblies drivably mounted onto said central shaft, means to retain said tooth assemblies in position on said central shaft, said means to retain said tooth assemblies on said central shaft being removal to permit replacement of tooth assemblies on said central shaft.

5. The combination specified in claim 1 wherein said from support means from said main frame comprises a rotatable front roller of substantial diameter to provide flotation over a snow surface.

6. The combination specified in claim 2 and spring tooth means on said main frame movable to engage the snow ahead of said rotor and to break said snow into chunks prior to engagement of the snow by said rotor.

7. The combination specified in claim 1 wherein said means to mount said rotor and feed bar member includes a rotor housing comprising a formed plate overlying said rotor, end plate members fixed to said formed plate, said end plate members extending from said formed plate downwardly to support said feed bar member and said rotor as a unit.

8. The combination specified in claim 2 wherein at least some of said rotor teeth are offset in an annular direction from others of said rotor teeth.

9. The combination specified in claim 4 wherein each of said rotor tooth assemblies have four radially extending teeth, and wherein some of said rotor tooth assemblies are annularly offset from others of the rotor teeth assemblies.

10. The combination as specified in claim 1 wherein said rear support means comprises a tubular roller member, disc plate means at the ends of said tubular roller member, said disc plate means being fixed to said tubular roller member and projecting radially outwardly beyond the outer surface of said tubular roller member a short distance to provide lateral stability when the tubular roller member engages the snow.

11. The combination as specified in claim 1 and a plurality of spaced planar members extending downwardly from said feed bar and fixed to said feed bar, said planar members extending in fore and aft direction with respect to direction of movement of said machine to form narrow vertically depending guide blades extending downwardly from said feed bar.

12. The combination specified in claim 6 and separate hydraulic cylinder means for alternately raising said spring tooth means away from the surface of said snow and forcing said spring tooth means into the snow.

13. The combination specified in claim 1 wherein said main frame includes means to permit said main frame to be towed behind a vehicle towing, a power source on said main frame, and wherein said power source supplies the power means for rotating said rotor and for pivoting said subframe relative to the main frame.

14. A snow conditioning machine comprising a main frame member having front and rear ends, a first transversely extending elongated roller rotatably mounted on said main frame member in position to support the front end of said main frame member, a subframe assembly positioned at the rear end of said main frame member, said subframe assembly being pivotally mounted to said main frame member about a first axis extending transverse to the normal direction of movement of said machine in use, a rotor, means to rotatably mount said rotor to said subframe assembly, said rotor comprising an axial shaft rotatable about a second axis transverse to the normal direction of movement of said machine, a plurality of substantially radially extending teeth spaced axially along said shaft, a second transversely extending elongated support roller rotatably mounted to said subframe assembly to the rear of said rotor, means to mount said second support roller at a position in respect to the first axis so that when said subframe assembly is in a first pivotal position with respect to said main frame member said rotor will be in position to engage snow as the main frame member is moved along snow being conditioned, and said second support roiler will be spaced from the snow to the rear of said rotor, and in a second position of said subframe assembly said second support roller will be engaging the snow to support the rear portions of said main frame member and said rotor, and said rotor will be spaced from said snow, means to direct snow into the path of rotation of said rotor, power means to rotate said rotor, and power means to control movement of said subframe assembly between its pivotal positions.

15. The combination specified in claim 14 wherein said means to direct snow into the path of said rotor comprises a transverse bar member fixedly mounted on said subframe below said rotor and engaging and being supported by snow over which the main frame moves when the subframe is in its first pivotal position with the second roller spaced from said snow.

16. The combination specified in claim 15 and a plurality of substantially uprightly extending teeth mounted on said transverse bar, said upright teeth being positioned to pass between teeth on said rotor as said rotor rotates.

17. The combination specified in claim 16 and means teeth mounted on said main frame to engage snow ahead of said rotor in the direction of normal travel of said main frame to break said snow into chunks prior to the time snow engages said rotor.

18. The combination specified in claim 16 and removable means to mount a plurality of said upright teeth and means to mount said removable means onto said transverse bar member.

- g g I UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIQN Patent No. 3,794,122 Dated Februarv 26. 1974 Inventor(s) Dennis L. Rohrer It is certified that error appears inthe above-identified patent and that said Letters Patent are hereby corrected as shown below;

r- In the abstract, line 9 passes" should be --passed-- Column 8, line 5 (Claim 13, line 3) "vehicle towing" should I be --towing vehicle-- Column 8, line 54 (Claim 17, linel) before "means" insert --teeth--; Column 8, line 55 (Claim 17, line 2) cancel .'teeth".

Signed and sealed this 16th day of July 1974.

(SEAL) Attest: v MccoY M. GIBSON, JR. 0. MARSHALL DANN Attesting Officer Commissioner of Patents

Claims

1. A snow conditioning apparatus comprising a vehicle having a main frame adapted to be moved over the surface of snow including front support means at a front portion of the vehicle, and a subframe assembly pivotally mounted to said main frame to the rear of said front support means, rear support means mounted on said subframe assembly at the rear of said vehicle, a snow conditioning section mounted on said subframe assembly comprising a rotor, means to rotatably mount said rotor to said subframe assembly about an axis substantially transverse to the direction of movement of said vehicle, said rotor including a plurality of axially spaced radially extending rotor teeth along the axial length thereof, power means to rotate said rotor at a desired speed to comminute snow coming in contact with said teeth as the rotor is rotated, a transverse support and feed bar member narrow in front and rear direction, means to mount said feed bar member on said subframe assembly in fixed position with respect to said rotor and below said rotor, said rear support means being mounted to said subframe assembly rearwardly of said rotor in direction of normal movement and on the opposite side of the pivotal mounting of the subframe assembly to the main frame from said rotor, power means to pivot said subframe assembly about its pivotal mounting to said main frame to selectively move said rotor away from said snow and support the rear portions of said main frame on said rear support means, and alternately to lift said rear support means from said snow and move said feed bar member into engagement with said snow to push snow toward said rotor as said vehicle is moved while supported by the snow.

5. The combination specified in claim 1 wherein said front support means from said main frame comprises a rotatable front roller of substantial diameter to provide flotation over a snow surface.

14. A snow conditioning machine comprising a main frame member having front and rear ends, a first transversely extending elongated roller rotatably mounted on said main frame member in position to support the front end of said main frame member, a subframe assembly positioned at the rear end of said main frame member, said subframe assembly being pivotally mounted to said main frame member about a first axis extending transverse to the normal direction of movement of said machine in use, a rotor, means to rotatably mount said rotor to said subframe assembly, said rotor comprising an axial shaft rotatable about a second axis transverse to the normal direction of movement of said machine, a plurality of substantially radially extending teeth spaced axially along said shaft, a second transversely extending elongated support roller rotatably mounted to said subframe assembly to the rear of said rotor, means to mount said second support roller at a position in respect to the first axis so that when said subframe assembly is in a first pivotal position with respect to said main frame member said rotor will be in position to engage snow as the main frame member is moved along snow being conditioned, and said second support roller will be spaced from the snow to the rear of said rotor, and in a second position of said subframe assembly said second support roller will be engaging the snow to support the rear portions of said main frame member and said rotor, and said rotor will be spaced from said snow, means to direct snow into the path of rotation of said rotor, power means to rotate said rotor, and power means to control movement of said subframe assembly between its pivotal positions.