US 3692132 A
Description (OCR text may contain errors)
United States Patent Pollanen  IMPROVED MOTOR SLEDGE Kyosti Johannes Pollanen, Isokyla,
Finland  Assignee: Velsa 0y, Kurikka, Finland  Filed: April 26, 1971  Appl. No.: 137,477
 Foreign Application Priority Data April 27, 1970 Finland ..l 168  US. Cl ..,..l80/5 R, 180/954, 305/20, l 305/27  Int. Cl ..B62m 27/02, B62d 55/16  Field of Search....305/20, 27, 10; 180/924, 9.2, 180/954, 9.32
 References Cited UNITED STATES PATENTS 3,157,913 11/1964 Habert .L' "ISO/9.24 R
[ Sept. 19, 1972 3,447,621 6/1969 Schoonover ..l80/9.64 R
FOREIGN PATENTS OR APPLICATIONS 842,862 3/1939 France ..305/22 Primary Examiner-Richard J. Johnson Attorney-Albert M. Parker 57 ABSTRACT ln a motor sledge having a supplementary frame extending from the rear end of the frame construction and flexibly pivoting around a horizontal axis the slackening of the common drive belts due to upward movement of the supplementary frame is prevented by a pair of rolls freely rotatable above the point of pivotement. When the supplementary frame pivots upwardly the upper surface of the drive belts are pressed against the rolls.
2 Claims, 3 Drawing Figures PATENTEDszmmz 3,692 132 SHEEI 3 0F 3 r W (mm a! BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to the field of motor sledges having a supplementary frame.
2. Description of the Prior Art The disadvantage of fixed frame extensions is that on rough ground the front part of the sledge tends to dive into the slop when going uphill. Also, the steerability of a sledge with such a fixed extension frame is not good owing to the length and stiffness of the frame. In spite of the lengthened drive belt the pulling efficiency is not entirely desirable, since on uneven ground each part of the roller belt will not touch the ground with the same surface pressure. On hard, rough ground the long stiff frame has tended to brake under a slightly heavy driver. Furthermore, the desired decrease of the surface pressure of the roller belt against the ground has not been obtained in spite of the longer bearing surface, since it' has been necessary to support the extension frame with many kinds of supporting structures to reinforce the joint, and these structures have added to theweight of the extension part.
There are also different previously known snowvehicles in which the drive belt has been fitted around sprung roller wheels. It has been noted, however, that the part of the belt above the wheels in these known structures will slacken, in which case the grip between r the roller belt and the wheels weakens decisively.
SUMMARY OF THE INVENTION According to the invention there is provided an improved motor sledge having a hinged frame extension and limiting organs fitted against the upper surface of the drive belt and attached to the frameapproximately above the joint to prevent the drive belt from slackening at depressions, when the rear end of the frame extension rises.
It is advantageous if the limiting organs are two wheels rotating freely on each side of the frame around the same horizontal axis.
The frame extension according to the invention together with the original sledge form .one entity which follows the ground. Even at abrupt depressions the front part of the sledge rises easily uphill. The steerability of such a sledge is also good since, when tilted, the flexible frame tends to assimilate to the sharpness of the curve. As the frame follows the ground, the entire length of the lengthened drive belt gets a good grip of the ground and the pulling efficiencyis good in all positions because of the limiting organs. This is also why the sledge runs very well in soft snow, which was particularly noticeable in steep uphill tests in which it was compared with fixed frame extensions. Because of the ladder structure, the hinging, and the springing, a frame extension according to the invention can be constructed with small material thickness without decreasing the durability. In this case the weight of the frame extension remains as small as possible and the surface pressure of the lengthened drive belt considerably smaller than that in the previously known solutions.
DESCRIPTION OF THE DRAWINGS FIG. 1 shows a perspective view of the frame extension,
2 FIG. 2 shows the mounting scheme for the same frame-extension, and
FIG. 3 shows a motor sledge according to the invention at difl'erent ground positions.
DESCRIPTION OF THE PREF ERRED EMBODIMENT cording to the drawing, with the extension frame is attached to the sledge frame by screws, have beenfattached to the same axle by branch cotters. One set of wheels 6 has been attached by screws 5 to lobes 4. The frame extension has been fittedl at the axle of the wheels by spiral springs 7 provided with 'pins to the lobes welded to the lift bow of the sledge. The back axle wheels 8 have been sprung with swinging arms 9 and attached to the frame shafts by extensions 10 fitted inside the shaft. The ends of the axle of the limiting rolls ll of the drive belt have been attached by screws at the hinging of the frame extension to the frame of the sledge above the drive belt. The limiting rolls prevent, I
tension to its lowest position. The stiffness of the flexibility can be easily regulated according to the ground, r
the snow conditions, and the weight of the driver or the load to be carried by control plates to be added to the ends of the spiral springs.
When a frame longer than the frame extension according to the invention is desired, it can be obtained a by extending the frame shafts to correspond with the desired number of wheels.
The frame extension can be hinged to the sledge, frame even without the attachment pieces 3 that elevate the frame. In this case the ability of the frame extension to bend upwards, however, decreases when the inner space of the frame lowers. The frame extension can also be hinged to a separate axle behind the hindmost roller wheelsof the sledge.
With different applications an extension according to the invention suits most known sledge brands in which the motor is in the front of the sledge. A frame extension according to the invention can also be fitted to motor sledges with two belts.
What is claimed is:
1. An improved motor sledge of the type having a rigid frame construction; steering means attached to the front part of the frame construction for pivotable movement around a substantially vertical axis; a plurality of wheels rotatably mounted under the frame construction; a supplementary frame portion attached to the rear end of the frame construction for flexible pivotable movement around a horizontal axis therein and further provided with wheels; at least one common endless drive belt fitted around the wheels; a power 3 source fixed to the frame construction; and power ing.
2. The improved motor sledgeof claim 1, in which the means for preventing slackening of the drive belt comprise a pair of coaxial rolls rotatably mounted on opposite sides of the frame construction for preventing a pair of drive belts from slackening.
wards in order to prevent the drive belt from slacken-